Will the annual gap affect the placements

Results of the DDA monitoring program

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1 VOGELWELT 121: (2000) 87 Results of the DDA Monitoring Program Part I: Changes in the population of bird species in the settlements since 1989 Johannes Schwarz & Martin Flade Schwarz, J. & M. Flade 2000: Results of the German Common Birds Census. Part I: population changes of urban breeding birds since Vogelwelt 121: This paper presents the first detailed analysis of data from the German Common Birds Census (DDA-Monitoringprogramm), which was initiated in 1989 to detect population changes in relatively common breeding birds. Results for 24 typical species of urban habitats are presented here. Further analyzes of bird data of forests, agricultural lands, wetlands, and dry habitats will follow. For the first time the TRIM program (Statistics Netherlands) has been used for data processing. Background and ideas for statistical data analyzes are described. The results are not only focussing on the overall population changes in Germany, but also on the differences between eastern and western Germany both within and outside urban habitats. Out of the 24 species analyzed here, 7 species have clearly increased, (e.g. Blackcap and Blackbird) and 3 species most likely increased. On the other hand, 5 species clearly and 2 species properly have decreased mainly species nesting on buildings. Attention has to be paid to the fact that some currently increasing species are only recovering from a long-lasting, severe decline prior to species, which shower a stable or fluctuating population level during the study period, may do so on an extraordinarily high or low population level, respectively. In some species, e.g. Wood Pigeon, Blackbird, Blackcap and Magpie, urbanization is still in progress. Some species also show significant differences in population changes between western and eastern Germany, for which an interpretation is sometimes not possible. Key words: Population trends, birds of urban habitats, bird monitoring, Germany, TRIM analysis. 1. Introduction and question 1.1. Background and aim of this work Since 1989 the umbrella association of German Avifaunists (DDA) has been running a program to record changes in the population of more common German breeding bird species on the basis of standardized counts by volunteers from the DDA member associations (DDA monitoring program; FLADE & SCHWARZ 1992). The objective is, on the one hand, to establish an early warning system that shows us negative changes in the populations of even more frequent breeding bird species before the species in question appear on the Red List, and on the other hand, negative and positive changes in the populations of birds should provide information about ecological changes in the landscape, which are often without use birds are difficult to identify as indicators (indicator function; see FLADE & SCHWARZ 1996). From the beginning, it was planned to carry out a first, more detailed evaluation of the material obtained after a period of about 10 years; with this work the first part is presented. For pragmatic reasons, it was decided to initially publish this evaluation step by step in four parts in the VOGELWELT. This could then be followed by an updated overall version in book form. In coordination with the reports on the situation of birds in Germany, the breakdown is not based on a systematic sequence of species, but arranged according to landscape units. The following classification is provided: birds of human settlements (this work), birds of the forests, birds of the agricultural landscape, birds of the wetlands and dry habitats. Limitations to the informative value of the material to be considered Already in the introduction we would like to point out that when interpreting the results presented here, three There are significant restrictions to be taken into account: Although the material evaluated here is definitely the best and most comprehensive that is currently available from Germany for most of the species treated, it is not equally representative for the whole of Germany. For various reasons (see Chapter 2), material from the west and north-west was included in the analysis.

2 88 J. SCHWARZ & M. FLADE: Changes in the population of bird species in the settlements since 1989 as from eastern Germany (Fig. 1). The data situation is insufficient for the federal states of Bavaria and Baden-Württemberg. The current trends in southern Germany could therefore in some cases deviate considerably from the trends presented here. However, an analysis in this regard can only be carried out if, for example, the apparently available data from Baden-Württemberg is made available as completely as possible to a TRIM evaluation (see Section 3.2.). The trends presented here only apply to the reporting period from. It is therefore possible that species that have declined in the population over decades, but have currently stabilized or recovered at a low level, are shown here as having the same or increasing population. In the case of some species (e.g. redstart), other studies have shown that the current positive trend is a recovery after a long-lasting strong decline. In the evaluation presented here, only the more common species are taken into account, which as a rule were registered with a total of at least 100 individuals / year in the point-stop counting or with at least 20 territories / year in the territory mapping. The overall balance according to increasing, decreasing and constant species would possibly give a slightly different picture if the rare species were also included. Sub-samples, East-West comparisons The development of the breeding bird populations in the settlements is the focus of this analysis. For this purpose, 24 species were selected whose occurrence is concentrated in settlement habitats or which are particularly common in settlements. If the analysis found that the population development in settlements differs significantly from the development outside (in the open landscape), the material was evaluated separately according to partial samples for settlements and the other landscape types and compared. Fig. 1a: Distribution of all PS routes (1st number) and RK areas (2nd number) processed since 1989 within the framework of the DDA monitor program by federal state, regardless of the number of years processed. Distribution of total number of point count routes (PS, first figure) and territory mapping plots (RK, second figure) surveyed since 1989 in the German Common Birds Census per federal state (regardless of the number of survey years). Fig. 1b: Distribution of the PS routes (1st number) and RK areas (2nd number) processed in 1998 as part of the DDA monitor program by federal state. Distribution of total number of point count routes (PS, first figure) and territory mapping plots (RK, second figure) surveyed in 1998 in the German Common Birds Census per federal state.

3 VOGELWELT 121: (2000) 89 In addition, the material was checked for differences between geographical regions; However, this analysis has to be limited to the east-west comparison, since not enough material is available from the south of Germany for an evaluation. This east-west comparison, in which the data from the new federal states are compared with the data from the old federal states, makes sense for landscape-ecological reasons, since both the initial state of the landscape and the changes in the last 10 years in east and west Germany were very different. The landscape differs e.g. B. by the following important factors in east and west: The population density is on the large-area average in western Germany with 258.9 inhabitants / km 2 almost twice as high as in E-Germany including Berlin with 162 inhabitants / km 2; While in the northeast there are large-scale landscapes with less than 100 inhabitants / km 2, the population density in the W and SW (Ruhr area, Rhine-Main-Neckar area) reaches values ​​between 600 and over 1200 inhabitants / km 2 over a large area Cutting through traffic routes and urban sprawl (BUN- DESAMT FÜR NATURSCHUTZ 1999). Many settlements in East Germany around 1990 were characterized by old, often damaged or dilapidated buildings, which were increasingly restored and modernized in the 1990s; a comparably strong change did not take place in the west during this period; In addition, the appearance of East German settlements differs from the often sterile West German settlements due to a higher proportion of unsealed areas characterized by ruderal vegetation; rural settlements in the west have often developed into pure garden cities, while in the east they have an even more rural / agricultural character. Agriculture in the east was characterized by collective farms (agricultural production cooperatives, LPGs) with huge fields and large, concentrated farm buildings and areas (LPG sites), while family farms predominate in the west; at the same time the use of production resources (agrochemicals) was lower in the east for various reasons and the use of arable land was less intensive overall; in particular, in the east there were and are more unused areas, failure points, accompanying areas that have fallen out of intensive use, wet and dry biotopes, etc. (FLADE et al. in preparation; RÖSLER & WEINS 1996; GEORGE 1996); In addition, the crop composition and crop rotations differed considerably (e.g. in the east until 1990 more field forage cultivation and summer cereals, but much less oilseeds). Even after reunification, the agricultural landscapes of Eastern Germany were extensively used areas (especially in grassland) and due to much larger field structures, but also very high proportions of fallow land and EU set-aside areas (e.g. in regions with poor soils at times over 20%) characterized an increasingly high proportion of organic farming areas (FLADE et al. in preparation). 2. Material and methods 2.1. Material The data material evaluated here was mainly collected by volunteers from the member associations of the DDA. The choice of the examined areas and routes was left to the observers (for reasons and explanations see FLADE & SCHWARZ 1996); Only in Brandenburg does a paid and centrally controlled program exist in the large protected areas, which aims to record the biosphere reserves, national and nature parks there as representative as possible. The material consists on the one hand of the data of the point-stop-counts (abbreviated PS; method see 2.2.), On the other hand of those of the territory mapping (RK; see 2.2.). To a lesser extent, data from line taxation (LT) are also available, which, if methodologically possible, were included in the RK database, but otherwise still awaiting evaluation. The number of PS routes included in the evaluation per year rose from approx. 90 to over 250 in the reporting period, with a total of almost five-minute counts per year (Fig. 2). The spatial focus is on the one hand in Hamburg, Lower Saxony, North Rhine-Westphalia and Hesse, on the other hand in Brandenburg (Fig. 1). In the RK part of the program, between 60 and 85 areas were evaluated annually, although the data is often only reported with a delay of 1-4 years because of the considerable evaluation work to be carried out by the mappers; In contrast to the PS, Fig. 2: Number of PS routes processed annually (R) and total number of PS counts (Z) in Germany Yearly totals of surveyed point count routes and total number of counts in the German Common Birds Census in the period

4 90 J. SCHWARZ & M. FLADE: Changes in the population of bird species in the settlements since 1989 no steady increase in the available data per year, but a decrease in recent years (not shown), which should be compensated for by late registrations in the next few years . Most of the RK areas are in Brandenburg and Mecklenburg-Western Pomerania, the rest for the most part in North Rhine-Westphalia and Hesse (Fig. 1). In Baden-Württemberg, under the direction of the state bird protection station there, extensive data material was also collected, which, however, is mainly based on line taxation and for the most part has not yet been made available to an evaluation by the DDA. As a result, the chance to improve the geographical distribution and informative value of the data material has been wasted so far. The uneven spatial distribution of the routes and areas must be taken into account when interpreting the results.Methods Terrain methods The terrain methods used were described in more detail by FLADE & SCHWARZ (1992) and are only briefly explained here: With the strictly standardized PS, the should be at least 300 m away from each other, on five dates a year if possible (1-4 counting dates are also possible) all perceptible birds are counted for exactly five minutes. The distance between the birds and the metering point is irrelevant. The area around the counting stops is classified according to 20 different, predefined habitat types (assignment accurate to 10%). No distinction is made between possible breeding birds and migrants. The counting periods are in the second half of March, second April, first and second May and the first half of June (6th counting period in the mountains and selection with fewer than five counts per year see FLADE & SCHWARZ 1992). The counts may only take place under favorable weather conditions and in the morning. Only counts by the same observer are included in the evaluation. If the observer changes, the count counts as a new route. The RK data are collected according to the known methodological guidelines (for a synopsis, see FLADE 1994). Sample areas of ha in forests and settlements, ha in the open landscape and at least seven inspections per season are recommended. The areas should be able to be assigned as uniformly as possible to one of the 20 habitat types of the given key, or the evaluation should be carried out separately according to habitat types. In contrast to the PS, only safe and probable breeding birds are recorded in the RK. The recorded unit is not individuals, but breeding pairs or territories. The RK also only takes into account data that were collected by the same observer with approximately the same amount of time each year. Evaluation methods The reported data are continuously entered into a dbase database set up by J. SCHWARZ. The previous interim evaluations (FLADE & SCHWARZ 1992, 1996, 1999) were based on a so-called chain index: A stock index was calculated up and down from a specified starting year, in which only PS and RK data were included that were collected in at least two consecutive years . The TRIM program (Trends and Indices for Monitoring Data, PANNEKOEK & VAN STRIEN 1998) was used for the first time in the evaluation presented here. The TRIM program was specially developed in the Netherlands for the calculation and statistical testing of stock indices from monitoring programs, in particular for Dutch breeding bird monitoring. It offers the following decisive advantages over the chain index we have previously shown for the individual species: Not only data from year pairs (year-to-year comparisons), but all data are included in the evaluation. The program calculates a model curve of the population changes of a species from all data sets (including those with annual gaps). The modeling makes it possible to specify statistical spreads (confidence intervals) for each year; This information shows how safe or reliable the index values ​​are from a statistical point of view; the narrower the confidence interval, the more homogeneous and reliable the data. With TRIM it is possible to statistically secure long-term increases or decreases; TRIM also calculates whether changes in the course (slope) of index curves are statistically significant or not; Through various evaluation variants, non-significant changes (changepoints) can be hidden and a less differentiated but more reliable course of the index curve can be calculated; However, one major restriction must be taken into account: TRIM cannot make any statements about the representation of our test areas and routes. Due to the fact that in the DDA program each employee can independently choose the area or route to be examined, there may be inconsistencies in the data material, in particular due to three sources of error: The sample is geographically unevenly distributed (e.g. gaps in southern and central Germany , Clusters in the west, northwest and east); The different habitats are not represented proportionally to their actual occurrence; The areas and routes were not selected according to a random statistical principle (e.g. for each geographic region and each main type of landscape); as a result, it can be, for example, areas of ornithological interest or relatively intact areas are overrepresented in the material. From a statistical point of view, these shortcomings do not mean that the results of the DDA program are unusable.In particular, we have the following options for checking the informative value of our data: We can compare the RK data with the PS data; if the trends of these random samples, which are completely different in terms of methodology and geographical distribution, agree, this is a good indication of the reliability of the result.

5 VOGELWELT 121: (2000) 91 We can compare the results from different geographical regions or different landscape types (e.g. East-West comparisons and comparisons between settlement biotopes and free landscape in this work); if the status quo matches, there is no doubt about the informative value. If the courses are significantly different (check with TRIM), a biological interpretation must be sought; this can e.g. through more detailed analysis of our own data (see example goldfinch in Section 4.4.) or through the inclusion of further in-depth auto-ecological research results. Only if differences cannot be clearly interpreted from a biological point of view, a possible data error (e.g. too small or unrepresentative samples) must be assumed. We can weight our data and incorporate it into our index curves with weighted proportions. In this way, Germany can be divided into regions (e.g. west and east in this evaluation; separate evaluation for south / southwest not yet possible, see Chapter 2) and the approximate population size in these regions can be calculated using the population estimates available from the federal states. The monitoring data from these regions can then be weighted with the proportion of the population there in the total population. This can compensate for the unequal geographical distribution of the areas and routes. A similar, albeit computationally somewhat more complicated, procedure is possible for different types of landscape (weighting based on the settlement densities and the area share), but has not yet been used for the present evaluation. Some details are explained about the application of TRIM here. TRIM requires an integer count value for each observation site per year and species. In the case of the RK, this is given by the number of areas on a test area. With the PS, however, a counting route is used up to five times per season, in the following time segments: Period 1: Period 2: Period 3: Period 4: Period 5: Period 6: (for mountainous areas). The counting results are available separately for each inspection and are not aggregated to paper areas, as is the case with the RK. For the evaluation with TRIM, the procedure was as follows: The sum of the counting results of one type at all (or all selected) stops of a counting route for all counted counting dates of a year formed the integer count. This was weighted with the reciprocal of the number of counting appointments completed, i.e. 0.2 for five appointments. In the evaluation, species-specific counting periods were excluded in which significant migratory events or already the occurrence of flocks of young birds can be expected. The comparison of trends in the old and new federal states (east-west comparison) as well as inside and outside of settlements are always based on the point-stop data. When comparing habitats, on the one hand those stops were selected which, according to the counters' estimates, consist of at least 75% settlement biotopes (including gardens, cemeteries); on the other hand, all stops were selected that do not have any settlement biotopes. When evaluating with TRIM, the Effects for each time point model was always chosen. The FOREST test was used to test the significance of the covariables (here the east-west comparison and the comparison of stops in settlement biotopes versus stops without settlement biotopes). In the east-west comparison, in addition to the representation as an index curve in percentages based on the year 1994 as the 100% year, a graphic in absolute values ​​was calculated. A weighting factor was used separately for each of the old and new federal states, which corresponds to the proportion of the individuals observed in the point-stop count according to the TRIM model calculation in 1994 in the estimated total population in the region concerned. The estimated population sizes for the federal states are WITT et al. (1996, supplemented by letter-type communication). Example: in the first TRIM run, a total number of observed individuals of was given for 1994. The population estimate, on the other hand, amounts to breeding pairs corresponding to 1 million individuals, so that in the point-stop counting 1/500 of the estimated actual population was recorded (1 million / 2000). 500 was therefore entered as the weighting factor for the second TRIM run. It should be emphasized that this presentation is a matter of hypothetical values ​​or rough estimates, which can deviate more or less strongly from the real stock sizes. The graphics can, however, show the rough population trend in East and West Germany and make the approximate relationship between the two sub-populations visible. This enables a more realistic overall assessment of the population development for Germany. The sample size n given in the graphs relates to the number of areas or counting routes included in the evaluation, on which the species in question was detected in at least one year. 3. Results In the following, the results for the 24 selected, typical types of settlement are presented in systematic order. A summarized presentation and discussion takes place in section 5. Kestrel Falco tinnunculus: trend negative. - The PS data (Fig. 3a) show periodic fluctuations with maxima in 1990 and 1994 and minima in 1989, 1992 and 1997; Overall, a highly significant decrease averaging 4.3% per year can be determined. In the sub-program RK the species was recorded in too few numbers, which is why the index is not shown. The east-west comparison

6 92 J. SCHWARZ & M. FLADE: Changes in the population of bird species in the settlements since 1989 (Fig. 3b) shows significantly different population trends, especially over the period, but the differences are not significant due to the relatively small and heterogeneous data material from the East (see wide scatter in Fig. 3b). - The population curve from the data from the monitoring of birds of prey and owls for the period (MAMMEN & STUBBE 1999, 2000) is similar to the index curve for Eastern Germany in Fig. 3b, although the material from MAMMEN & STUBBE is much more extensive, but a clear focus in East has. According to MAMMEN & STUBBE (1999), the species initially increased sharply from 1988 to 1993, and then decreased significantly again from 1994 to 1997; In 1997/98 there was a significantly more pronounced increase in the population than can be derived from our PS data. According to BAUER & BERTHOLD (1996), the kestrel declined significantly in Central Europe by the mid-1980s; after that the species showed a more or less clear recovery. Fig. 4a: Stock index of the wood pigeon according to PS and RK data (PS: only counting periods 3 and 4). Population index of Wood Pigeon in Germany according to territory mapping (RK) and point count (PS) data. Mean annual change: RK: +1.7% ± 0.9% (p <0.05, n = 122); PS: -1.2% ± 0.5% (p <0.05, n = 438). Fig. 3a: Population index of the kestrel in Germany based on PS data, counting periods 1-4 (insufficient data from the RC). Population index of Kestrel in Germany according to point counts (insufficient data for territory mapping). Overall trend: -4.3% ± 1.1% per year (p <0.01, n = 345). Fig. 3b: Population index of the kestrel in West and East Germany based on PS data. Population index of Kestrel in West and East Germany according to point counts. Overall trends annual change: West West: -3.3% ± 1.1% (p <0.01; n = 231); East East: -2.8% ± 5.25% (0.05

7 VOGELWELT 121: (2000) 93 PS index, the decrease is significantly weaker, but still significant. The fact that the RK areas are mainly located in eastern Germany should play a role here: the east-west comparison of the PS data reveals a strong, highly significant decline in the population in the east (despite strong scatter with low data density), while the population in the west is almost remained the same, Fig. 5a: population index of the Turkish pigeon according to PS and RK data. Population index of Collared Dove in Germany according to territory mapping (RK) and point count (PS) data. Mean annual change: RK: -20.6% ± 0.5% (p <0.01; n = 22); PS: -3.0% ± 1.0% (p <0.05; n = 262). whereby the difference in the index curves is highly significantly different. This is confirmed by literature data (cf. also BAUER & BERTHOLD 1996): After Germany was first settled in the 1940s and an exponential population increase with a maximum in the early 1970s, the population in eastern Germany fell sharply again in many places. B. is very well documented for Berlin (WITT 1989, 1994, 2000). - The overall index, geographically weighted according to population size (Fig. 5c), shows a clear decrease, then a slight increase up to Common Swift Apus apus: increasing significantly in the west, significantly increasing in the east and decreasing quite strongly at the beginning. - Because of the small amount of data in the RK, only the PS data are suitable for an index calculation. Fig. 6a shows the contrasting developments in East and West Germany. Based on the index curves weighted geographically according to population size (Fig. 6b), it can be seen that the starting stock in 1989 in East Germany, which is much smaller in terms of area, was initially probably higher than the West German stock, Population index of Collared Dove in West and East Germany according to point counts. Overall trends - Annual change: West West: - 1.1% ± 1.2% (n.s .; n = 179); East East: -10.4% ± 2.0% (p <0.01, n = 83). Difference difference: p <0.01. Fig. 6a: Common swift population index in West and East Germany based on PS data. Population index of Swift in West and East Germany according to point counts. Overall trends - Annual change: West West: + 3.2% ± 1.2% (p <0.05; n = 210); East East: -6.2% ± 1.9% (p <0.01; n = 112). Difference difference: p <0.001. Fig. 5c: Population development of the Turkish pigeon in East Germany, West Germany and overall based on the absolute population sizes estimated in 1994. Population change of Collared Dove in East Germany, West Germany and in total, relative to population estimate in 1994 (= 100%). Fig. 6b: Development of the swift population in East Germany, West Germany and overall based on the absolute population figures estimated in 1994. Population change of Swift in East Germany, West Germany and in total, relative to population estimate in 1994 (= 100%).

8 94 J. SCHWARZ & M. FLADE: Changes in the population of bird species in the settlements since 1989 but then decreased to around a third of the West German population by 1998. The cause of this could be the intensive renovation work on damaged building structures in the east German cities after the fall of the Wall (removal of nesting opportunities, BRAUN 1999). The overall German development (Fig. 6b) shows no significant trend for the entire study period. The overall fairly even development is typical of the common swift as a species with a high life expectancy and low annual reproduction (BAUER & BERTHOLD 1996). Green woodpecker Picus viridis: Increasing in the reporting period. - PS and RK data show, apart from an initial clear discrepancy, very good agreement with surprisingly low scatter in each case in view of the low population density of the species (Fig. 7). In particular, the temporary population collapse (after the severe winters 1995/96 and 1996/97) and the subsequent strong population recovery are well documented by both methods. The population increase from 1989 onwards represents a recovery after a long-term significant decrease in western Central Europe and Scandinavia in the 1970s and 1980s (BAUER & BERTHOLD 1996). Stock developments inside and outside of settlements largely coincide, differences are not significant (not shown); This means that SÜDBECK's assumption (in BAUER & BERTHOLD 1996) that the species is withdrawing more and more from settlements into forest areas cannot be confirmed for the reporting period. Fig. 7: Stock index of the green woodpecker according to RK and PS data (PS: counting periods 1-4). Population index of Green Woodpecker in Germany according to territory mapping (RK) and point count (PS) data. Mean annual change: RK: +1.4% ± 3.8% (n.s .; n = 39); PS: + 4.0% ± 1.5% (p <0.05; n = 285). Barn swallow Hirundo rustica: Consistence constant. - The PS-Index fluctuates only very slightly with an overall very low spread; the RK data, on the other hand, are surprisingly heterogeneous with consistently very strong scatter (Fig. 8a). Also Fig. 8a: Stock index of the barn swallow according to RK and PS data (PS: counting periods 1-4). Population index of Swallow in Germany according to territory mapping (RK) and point count (PS) data. Mean annual change: RK: +1.4% ± 3.8% (n.s .; n = 39); PS: + 4.0% ± 1; 5% (p <0.05; n = 285). Fig. 8b: Stock index of the barn swallow in West and East Germany according to PS data. Population index of Swallow in West and East Germany according to point counts. Overall trends - Annual change: West West: 0.0% ± 0.8% (n.s .; n = 249); East East: -1; 5% ± 9; 5% (n.s .; n = 164). the east-west comparison (Fig. 8b) shows a curve that is significantly different in each individual case, but no significant trend in either region. Obviously, however, it is a matter of a leveling off of the population at a lower level after a clear decline in the 1970s and 80s, which SCHERNER (1999) describes for southern Germany and which, according to BAUER & BERT-HOLD (1996), is likely for all of Germany. House martin Delichon urbica: Population declining, particularly in western Germany. - Fig. 9a shows clearly different index curves for East and West Germany on the basis of the PS data, which are highly significantly negative for West Germany and only slightly negative for East Germany with initially strong scatter. The overall trend, weighted regionally according to stock sizes (9b), shows an almost continuous decrease for Germany. This development differs from the assessment of BAUER & BERTHOLD (1996), who estimate the population for the 1980s and early 1990s to be largely stable. Which increased in many large cities especially in the 1970s and 1980s

9 VOGELWELT 121: (2000) 95 Fig. 9a: Stock index of the house martin in West and East Germany according to PS data. Population index of House Martin in West and East Germany according to point counts. Overall trends - Annual change: West West: -3.6% ± 1.2% (p <0.01; n = 214); East East: - 2.7% ± 3.4% (n.s.; = N = 135). Difference in the course of the curve difference in index curve: p <0.01. Fig. 10: Stock index of the white wagtail according to RK and PS data (PS: counting periods 1-4). Population index of White Wagtail in Germany according to territory mapping (RK) and point count (PS) data. Mean annual change: RK: -5.1% ± 1.9% (p <0.05; n = 101); PS: -2.4% ± 0.6% (p <0.01; n = 420). similar after all partial samples (Fig. 11a-d): steep weather-related decreases in 1990/91 and 1995/96, in the other periods increase (population recovery). The PS and RK index curves agree well, but the RK curve is somewhat rotated, so that according to PS data there is a significant decrease overall, according to RK data, on the other hand, a highly significant decrease. West Germany and overall based on the absolute population sizes estimated in 1994.Population change of House Martin in East Germany, West Germany and in total, relative to population estimate in 1994 (= 100%). The observed increase in new high-rise housing estates as well as increasingly also in old building districts (e.g. BRAUN 1999; WITT 2000) is therefore a sign of urbanization (relocation of the stock from villages to cities with apartment blocks) and has not been accompanied by a general stock increase at least since 1990 hand in hand. White wagtail Motacilla alba: Significant decrease / 96. - Although the index curves according to RK and PS data are clearly different at the beginning (Fig. 10), both curves agree in their strongly negative trend, especially in the first half of the reporting period; this development does not correlate with the occurrence of cold winters, as was otherwise determined several times by BAUER & BERTHOLD (1996). In contrast, there are no significant differences between East and West or between settlements and open land. Wren Troglodytes troglodytes: All in all, the population remains roughly the same, with strong populations after cold winters. - The course of the curve is Fig. 11a: Stock index of the wren according to RK and PS data (PS: counting periods 1-4). Population index of Wren in Germany according to territory mapping (RK) and point count (PS) data. Mean annual change: RK: +5.6% ± 1.2% (p <0.01; n = 126); PS: -2.1% ± 0.4% (p <0.05; n = 420). Fig. 11b: Population index of the wren in West and East Germany according to PS data. Population index of Wren in West and East Germany according to point counts. Overall trends - Annual change: West West: -2.4% ± 0.4% (p <0.01, n = 268); East East: + 3.6% ± 2.3% (n.s .; n = 152). Difference difference: p <0.01.

10 96 J. SCHWARZ & M. FLADE: Population changes of bird species in the settlements since 1989 Fig. 11c: Population index of the wren inside and outside of settlements according to PS data. Population index of Wren within and outside urban habitats. Mean annual change annual change: Settlements urban habitats: +0.4% ± 0.9% (n.s .; n = 166); outside settlements outside urban habitats: -2.7% ± 0.4% (p <0.01; n = 401). Difference difference: p <0.05. Fig. 11d: Population development of the wren in East Germany, West Germany and overall based on the absolute population size estimated in 1994. Population change of Wren in East Germany, West Germany and in total, relative to population estimate in 1994 (= 100%). Increase (Fig. 11a). The cause of this difference is obviously the east-facing distribution of the RK areas, because the PS data separated into east and west show the same, highly significant difference (Fig. 11b). The reason could be that most of the East German populations move away in winter and are therefore not as sensitive to cold winters. Fig. 11c also shows that the population remained more or less constant with the same overall pattern in the settlements, while a highly significant negative trend can be discerned overall in the open landscape. The development in settlements and in East Germany was therefore more favorable than overall. The regionally weighted overall trend (Fig. 11 d) results in a strongly fluctuating, overall constant trend due to the weather, whereby the species is much more common in the Atlantic climate region of western Germany than in eastern Germany. Black redstart Phoenicurus ochruros: population constant. - The PS data show a little fluctuating, overall constant population Fig. 12: Black redstart population index according to RK and PS data (PS: counting periods 1-4). Population index of Black Redstart in Germany according to territory mapping (RK) and point count (PS) data. Mean annual change: RK: -4.0% ± 3.4% (n.s .; n = 49); PS: 0.0% ± 0.7% (n.s .; n = 373). (Fig. 12). The RK data, which are surprisingly widely scattered, do not deviate significantly from this overall, but document the obviously very different local population trends. Redstart Phoenicurus phoenicurus: Population increasing in the reporting period (recovery after previous strong decline). - Both RK and PS data show a significant increase from 1992 at the latest, which is also highly significant for the PS data (Fig. 13). Obviously this is a recovery after decades of, sometimes dramatic, population decline, especially in the 1950s to 1970s (synoptic representation in BAUER & BERTHOLD 1996, evaluation of settlement density data see FLADE 1994). East-west or city-open country differences are not detectable. This indicates that the main factors for the population development are in the migration and wintering areas, especially in the Sahel zone (BAUER & BERTHOLD 1996). Fig. 13: Redstart population index according to RK and PS data (PS: counting periods 3-5). Population index of Common Redstart in Germany according to territory mapping (RK) and point count (PS) data. Mean annual change: RK: + 3.4% ± 2.9% (n.s .; n = 62); PS: + 4.5% ± 1.2% (p <0.01; n = 267). Blackbird Turdus merula: Increasing, especially in the settlement area. - Although the curves in the

11 VOGELWELT 121: (2000) 97 according to the (little scattering) PS data in the settlement area, the population development in the period clearly different from the open landscape (Fig.14c): While the population outside the settlements remained more or less constant, the blackbird in Settlement areas increased particularly in the period. This can be seen as evidence that the urbanization of the species continues (cf. BAUER & BERTHOLD 1996). Fig. 14a: Stock index of the blackbird according to RK and PS data (PS: counting periods 1-3). Population index of Blackbird in Germany according to territory mapping (RK) and point count (PS) data. Mean annual change: RK: +1.6% ± 0.6% (p <0.05; n = 144); PS: +0.8% ± 0.3% (p <0.05; n = 442). Song thrush Turdus philomelos: Constant or slightly decreasing. - While the PS data show a highly significant decrease, the RK data, which are much more scattered, give no indication of a decrease (Fig. 15a). It should be borne in mind here that the species has in some cases significantly decreased in Western and Northern Europe (particularly well documented for Great Britain, THOMSON et al. 1997). However, in contrast to the RK index, the PS index could be clearly influenced by Scandinavian migrants who cannot be sufficiently separated from breeding birds using the PS method. - The population development in and outside of settlements (Fig. 15b) as well as in east and west Fig. 14b: Population development of the blackbird in East Germany, West Germany and overall based on the absolute population sizes estimated in 1994. Population change of Blackbird in East Germany, West Germany and in total, relative to population estimate in 1994 (= 100%). Fig.15a: Stock index of the singing throttle according to RK and PS data (PS: counting periods 2-4). Population index of Song Thrush in Germany according to territory mapping (RK) and point count (PS) data. Mean annual change: RK: + 1.1% ± 1.2% (n.s .; n = 135); PS: -2.1% ± 0.5% (p <0.01; n = 426). Fig. 14c: Stock index of the blackbird inside and outside of settlements according to PS data. Population index of Blackbird within and outside urban habitats. Mean annual change annual change: Settlements urban habitats: + 2.8% ± 0.5% (p <0.01; n = 222); outside settlements outside urban habitats: 0.0% ± 0.4% (n = 424). Difference difference: p <0.001. Are different in detail, both PS and RK data confirm the increase in the reporting period (Fig. 14a). Since the blackbird is much more common in the west than in the east, the highly significantly different population changes in the east hardly affect the overall German trend (see geographically weighted overall trend in Fig. 14b). Fig. 15b is interesting: population index of the song thrush inside and outside of settlements according to PS data. Population index of Song Thrush within and outside urban habitats. Mean annual change annual change: Settlements urban habitats: -1.2% ± 1.1% (n.s .; n = 165); outside settlements outside urban habitats: -1.4% ± 0.6% (p <0.05; n = 416). Difference difference: n.s.

12 98 J. SCHWARZ & M. FLADE: Changes in the population of bird species in the settlements since 1989 in Germany (not shown) are not significantly different. This means that - unlike the blackbird - no further urbanization can be seen in the reporting period. Yellow Mocker Hippolais icterina: Population slightly (not significantly) decreasing or constant. - The index curves according to RK and PS data (Fig. 16) are relatively very different, but both show a rather negative trend - this is not significant, however. However, BAUER & BERTHOLD (1996) describe a significant loss of land in southern Germany since the late 1960s, while in northern Germany, in eastern central Europe and Scandinavia the stocks remained stable or even increased in the 1980s. - All in all, the data for both index curves are very scattered. East-west differences are not significant, the development in and outside of the settlements is almost identical. Blackcap Sylvia atricapilla: Increasing strongly. - RK and PS indices show the population increase in very good agreement, which is only interrupted by short-term, slight decreases (Fig. 18a). Both favorable habitat changes and (above all) the gradual relocation of winter quarters from the Mediterranean to Great Britain with the shortening of migration routes and the associated reduction in winter mortality are responsible for the positive development (BAUER & BERTHOLD 1996). The interim lows of 1991 and 1996 can lead to unusually cold and long winters (especially Fig. 18a: Blackcap population index according to RK and PS data (PS: counting periods 2-6). Population index of Blackcap in Germany according to territory mapping (RK) and point count (PS) data.Mean annual change: RK: +3.7% ± 0.8% (p <0.01; n = 144); PS: +3.8% ± 0.3% (p <0.01; n = 437). Fig. 16: Population index of Icterine Warbler in Germany according to territory mapping (RK) and point count (PS) data.Mean annual change: RK: -3.3% ± 2.0% (ns; n = 81); PS: -1.5% ± 0.9% (ns; n = 292). Rattle warbler Sylvia curruca: Fluctuating, overall declining - RK and PS indices show quite good agreement (Fig. 17) The trend is declining overall, with a first low at the beginning of the 1990s and an interim high in the period significant East-West Unt Different or different developments inside and outside of settlements cannot be determined. Fig. 18b: Blackcap population index inside and outside of settlements according to PS data. Population index of Blackcap within and outside urban habitats. Mean annual change annual change: Settlements urban habitats: + 7.1% ± 0.9% (p <0.01; n = 192); outside settlements outside urban habitats: +3.1% ± 0.4% (p <0.01; n = 419). Difference difference: p <0.01. Fig. 17: Stock index of the rattle warbler according to RK and PS data (PS: counting periods 3-6). Population index of Lesser Whitethroat in Germany according to territory mapping (RK) and point count (PS) data. Mean annual change: RK: -7.3% ± 2.7% (p <0.05; n = 94); PS: -1.6% ± 1.0% (n.s .; n = 348).

13 VOGELWELT 121: (2000) / 96) can be explained in Central and Western Europe (cf. parallel development with the wren!). It is interesting that the increase in the settlement area is much more pronounced than in the open landscape, i.e. the general increase is also associated with increasing urbanization (Fig.18b). The population trend in the east and west is the same. Blue tit Parus caeruleus: Probably a positive trend, especially in settlements. - The RK data show an almost constant population with a relatively low overall spread, while the PS index is clearly positive, with its lowest point in 1989 and maximum in 1996, since then it has decreased again (Fig. 19a). Declines in stocks after cold winters (BAUER & BERTHOLD 1996) are not discernible in the index curves. After significant increases and expansion over the course of this century, the population in Germany has been estimated to be constant over the last few decades (BAUER & BERTHOLD 1996). In spite of the good overall agreement of the partial samples, the trend in settlements is significantly more positive than outside (Fig. 19b). Great tit Parus major: Probably positive trend, especially in settlements. - As with the blue tit, an increase is only significant according to the PS data (Fig. 20a), and is more pronounced in the settlements than outside (Fig. 20b). Fig. 20a: Stock index of the great tit according to RK and PS data (PS: counting periods 1-3). Population index of Great Tit in Germany according to territory mapping (RK) and point count (PS) data. Mean annual change: RK: +0.53% ± 0.71% (n.s .; n = 151); PS: + 2.3% ± 0.4% (p <0.01; n = 439). Fig. 19a: Stock index of the blue tit according to RK and PS data (PS: counting periods 1-3). Population index of Blue Tit in Germany according to territory mapping (RK) and point count (PS) data. Mean annual change: RK: +0.4% ± 0.7% (n.s .; n = 144); PS: + 2.3% ± 0.5% (p <0.01; n = 434). Fig. 20b: Stock index of the Kohlmese inside and outside of settlements according to PS data. Population index of Great Tit within and outside urban habitats. Mean annual change annual change: Settlements urban habitats: +3.1% ± 0.7% (p <0.01; n = 224); outside settlements outside urban habitats: +1.4% ± 0.5% (p <0.01; n = 420). Difference in the curve difference in index curve: p <0.001. Fig. 19b: Index of the blue tit population inside and outside of settlements according to PS data. Population index of Blue Tit within and outside urban habitats. Mean annual change annual change: Settlements urban habitats: +3.2% ± 0.7% (p <0.01: n = 214); outside settlements outside urban habitats: +1.4% ± 0.6% (p <0.05; n = 413). Difference difference: p <0.05. Fig. 20c: Population development of the great tit in East Germany, West Germany and overall based on the absolute population sizes estimated in 1994. Population change of Great Tit and in East Germany, West Germany and in total, relative to population estimate in 1994 (= 100%).

14 100 J. SCHWARZ & M. FLADE: Changes in the population of bird species in the settlements since 1989 due to the influence of cold winters cannot be identified. The very clear (highly significant) difference in the population trend in eastern and western Germany over the period has only a relatively minor effect on the overall trend, which is geographically weighted according to population size (Fig. 20c). Elster Pica pica: Overall, the population remains the same with ongoing urbanization. - Due to the low data density and locally very different inventory changes, the RK data show extremely wide scatter ranges with an overall roughly constant trend (Fig. 21a). The scatter in the PS data, on the other hand, is small. After 1994, the PS index is still positive in settlements, but strongly negative in the open countryside (Fig. 21b). Overall, these trends seem to balance each other out. Hunting of the species that is not permitted in settlements for legal reasons is not only superfluous and unfounded in the open countryside, but also reinforces the trend of disappearing from the open landscape and increasing concentration in the settlements. Carrion crow Corvus corone: Increase especially in western Germany. - The RK data, which, as in the case of the Elster, have large spreads, remain un- Fig. 22a: Crows population index in West and East Germany according to PS data. Population index of Carrion and Hooded Crow in West and East Germany according to point counts. Overall trends - Annual change: West West: + 4.2% ± 0.5% (p <0.01; n = 172); East East: + 2.0% ± 1.9% (n.s .; n = 172). Difference difference: p = 0.0001. Fig. 21a: Elster population index according to RK and PS data (PS: counting periods 1-6). Population index of Magpie in Germany according to territory mapping (RK) and point count (PS) data. Mean annual change: RK: -3.1% ± 2.7% (n.s .; n = 56); PS: - 0.2% ± 0.6% (n.s .; n = 347). Fig.22b: Population index of Carrion and Hooded Crow within and outside urban habitats according to PS data. Mean annual change annual change: Settlements urban habitats: +3.6% ± 1.1% (p <0.01; n = 196); outside settlements outside urban habitats: + 3.7% ± 0.6% (p <0.01; n = 415). Difference difference: n.s. Fig. 21b: Elster population index inside and outside of settlements according to PS data. Population index of Magpie within and outside urban habitats. Mean annual change annual change: Settlements urban habitats: +3.6% ± 1.1% (p <0.01; n = 224); outside settlements outside urban habitats: -1.4% ± 1.3% (n.s .; n = 420). Difference difference: p <0.01. Fig. 22c: Population development of the carrion crows in East Germany, West Germany and overall based on the absolute population sizes estimated in 1994. Population change of Carrion and Hooded Crow in East Germany, West Germany and in total, relative to population estimate in 1994 (= 100%).

15 VOGELWELT 121: (2000) 101 considered.The PS data show an almost continuous increase in western Germany (carrion crow C. c. Corone), whereas in the east (hooded crow C. c. Cornix) the population remained the same overall with much greater fluctuations and scattering (Fig. 22a). In contrast to the Elster, further urbanization cannot currently be proven on the basis of our data (Fig. 22b). The overall trend, geographically weighted according to population size (Fig. 22c), results in a total population growth of 20% for the reporting period, with population changes that differ between East and West. Star Sturnus vulgaris: persistence constant. - If the course of the index curves differ in detail, both the PS and the RK data result in a constant inventory (Fig. 23). The comparisons (not shown) between east and west as well as between settlements and open countryside do not show a significant increase or decrease for any of the subsamples, in some cases with different curves. It is possible, however, that the population has leveled off at a lower level after a previous significant decline; According to BAUER & BERTHOLD (1996), the population has been declining strongly, especially in north-west and north-east Europe, to a lesser extent regionally but also in central Europe. Fig. 23: Star population index according to RK and PS data (PS: counting periods 1-3). Population index of Starling in Germany according to territory mapping (RK) and point count (PS) data. Mean annual change: RK: -0.41% ± 0.78% (n.s .; n = 123); PS: +1.7% ± 1.0% (n.s .; n = 433). House Sparrow Passer domesticus: Population likely to be in decline. - Hardly any other species show such differences in the curve progression between PS and RK data (Fig. 24a). It must be taken into account here that the non-territorial house sparrow which breeds in colonies is a species that is difficult to quantify (see e.g. BRAUN 1999). The recording problems with the PS are likely to be significantly greater than with the RK: While with the RK entry points at buildings or nests can be searched for and counted systematically, with the PS often the fig. 24a: Stock index of the house sparrow according to RK - and PS data (PS: counting periods 1-3). Population index of House Sparrow in Germany according to territory mapping (RK) and point count (PS) data. Mean annual change: RK: -13.1% ± 2.5% (p <0.01; n = 174); PS: -0.8% ± 0.6% (n.s .; n = 355). Fig. 24b: Population development of the house sparrow in East Germany, West Germany and overall based on the absolute population size estimated in 1994. Population change of House Sparrow in East Germany, West Germany and in total, relative to population estimate in 1994 (= 100%). the exact number of sparrows in the vicinity of the stops (and often only audible) can hardly be determined. It is therefore to be assumed that the strong decline in stocks represented by RK data is more in line with reality. It is also expressed in the overall trend according to PS data, weighted geographically according to stock size (Fig. 24b). Fig. 24b also shows that despite the different area sizes, the absolute population estimates in East and West Germany are almost the same. - As BRAUN (1999) has shown, the house sparrow reacts to the renovation of old buildings with severe populations, as nesting opportunities are lost on the previously damaged building structures. On the other hand, according to WITT (2000), at least in Berlin, this is more than compensated for by the increasing number of nesting opportunities in prefabricated buildings and aging new housing developments. Overall, however, there are increasing research findings that indicate strong local and regional population declines in western Europe (e.g. BAUER & BERTHOLD 1996; BOWER 1999; MITSCHKE et al. 1999; MITSCHKE et al. 2000; SUMMERS-SMITH 2000) .

16 102 J. SCHWARZ & M. FLADE: Changes in the population of bird species in the settlements since 1989 Girlitz Serinus serinus: Increasing in the west, constant in the east. PS and RK index curves run roughly parallel, with the scatter of the RK data being quite large due to the small amount of data (Fig. 25a). The increase is therefore only significant for the PS index. The separate analysis of west and east shows a significant increase in the west and the same population in the east (not shown). Since the East German population only makes up about a third to a quarter of the total German population, the trend weighted geographically according to the estimated population size is positive for the whole of Germany (Fig. 25b). After Germany was resettled in the 1930s to 1970s, populations have declined significantly again, particularly in the northwest, since the late 1970s (MITSCHKE et al. 2000; Synopsis in BAUER & BERTHOLD 1996). Overall, however, the species is still spreading in Europe. Fig. 26a: Stock index of the greenfinch according to RK and PS data (PS: counting periods 1-3). Population index of Greenfinch in Germany according to territory mapping (RK) and point count (PS) data. Mean annual change: RK: + 6.9% ± 1.5% (p <0.01; n = 114); PS: +1.3% ± 0.7% (n.s .; n = 427). Fig. 25a: Population index of the Girlitzes according to RK and PS data (PS: counting periods 1-3). Population index of Serin in Germany according to territory mapping (RK) and point count (PS) data. Mean annual change: RK: +5.3% ± 3.3% (n.s .; n = 41); PS: + 3.3% ± 1.4% (p <0.05; n = 282). Fig. 25b: Development of the Girlitz population in East Germany, West Germany and overall based on the absolute population size estimated in 1994. Population change of Serin in East Germany, West Germany and in total, relative to population estimate in 1994 (= 100%). Fig. 26b: Population development of the greenfinch in East Germany, West Germany and overall based on the absolute population sizes estimated in 1994. Population change of Greenfinch in East Germany, West Germany and in total, relative to population estimate in 1994 (= 100%). Greenfinch Carduelis chloris: Overall, probably increasing. The rise in the index curves is only significant and much more pronounced for the RK index (Fig. 26a). The geographically weighted overall development in Germany according to PS data with individually different courses in east and west is shown in Fig. 26b. This fits into the existing picture: Despite local, and in some cases also regional, declines, BAUER & BERTHOLD (1996) still assess the population trend overall as increasing. Goldfinch Carduelis carduelis: Increasing particularly strongly in the mid-1990s. The species illustrates an example of the weaknesses of the PS method: The index curve according to RK data is highly significantly positive, with a strong increase particularly over the period (Fig. 27). The PS index for counting periods 1-4 initially runs quite well in parallel, but then runs in the opposite direction in the section (Fig. 27). An analysis of the data showed that in March 1994 unusually large goldfinch troops were recorded, which were evidently not formed by breeding birds but by non-breeding troops on fallow fields. Such late winter accumulations were not recorded at all in 1995. When the counting period I is hidden, the PS index equals

17 VOGELWELT 121: (2000) 103 Fig. 27: Stock index of the goldfinch according to RK and PS data (PS: counting periods 1-4 and 2-4). For the 1994 peak in the PS index for counting periods 1-4, see text. Population index of Goldfinch in Germany according to territory mapping (RK) and point count (PS) data. For interpretation of the peak in point count data (periods 1-4) in 1994 see text. Mean annual change: RK: + 9.4% ± 2.6% (p <0.01; n = 79); PS: + 2.5% ± 1.5% (n.s .; n = 344). already very close to the RK index (Fig. 27, PS 2-4). This shows that for species that regularly appear in non-breeding groups during the counting season, the RK index is more meaningful and the PS index can lead to false conclusions if the data is not carefully analyzed. Since there are no significant differences in trends either in an east-west comparison or in a settlement-free landscape comparison, it can be assumed that the urbanization of the goldfinch (gains especially in urban areas, BAUER & BERTHOLD 1996) is apparently no longer continuing. 4. Summary discussion 4.1. Overall population trends The analysis of the 24 typical bird species in cities and villages shown here shows that, similar to the 75 rarest German breeding bird species (MÄDLOW & MODEL 2000), species with (rather) positive trends predominate (Tab. 1). The seven species that were clearly increasing in the reporting period, however, include the green woodpecker and the common redstart, two species that had declined dramatically over the long term before 1990. While periods of drought in the Sahel zone were evidently of great importance for the common redstart, the causes for the green woodpecker are more likely to be found in habitat changes in the breeding areas (BAUER & BERTHOLD 1996). It can be seen that blackbird, blackcap, greenfinch, great tit and blue tit are the most common ubiquists among the increasing species; there is thus also a trend towards more and more birds among the settlement followers (for parallel findings for western Schleswig-Holstein see BUSCHE 1999). For a long time, there have been more or less strong urbanization tendencies for the species mentioned (cf. 5.2). On the other hand, the actual building breeders and key species of the settlements (according to FLADE 1994), i.e. the settlement specialists, show constant (common swift, barn swallow, black redstart) and even mostly decreasing trends (house sparrow, kestrel, house martin, turkish dove). Despite the ongoing expansion of the settlements in terms of area, the settlement specialists are not doing better, but rather worse! The reasons for this development are largely known: Many building breeders lose nesting opportunities with increasing maintenance and renovation of the building fabric. In addition, village structures with animal husbandry and open stables are declining. B. offer favorable feeding conditions for the swallow species, house sparrow and turkish dove (cf. synoptic representation in FLADE 1994) Comparison of settlements in the open landscape For some species the population development in the settlements (towns and villages) differs from that in the habitats of the open landscape (mainly forests and Agricultural landscape) significantly different. In the case of the wren, for example, the development in the settlements is more favorable with an overall similar population trend. This also applies to blackbird, cabbage and blue 1990 (++) Rather increasing than constant (+) Population constant or fluctuating without a significant trend Rather decreasing than constant (-) Clearly decreasing (-) Blackbird Blackcap Carrion Crow Giritz Goldfinch Green Woodpecker Redstart Blue tit Great tit Greenfinch Wood pigeon Common swift Barn swallow Black swallow Magpie Star Song Thrush House Sparrow Kestrel Turkish Pigeon House Martin Wagtail Wagtail Rattle Warbler