Breeding Bird Populations Research Articles

Effects of environmental pollution on breeding populations of birds in southern Poland

Breeding performance of Great tit (Parus major) was studied in two forests in southern Poland, in the districts of Cracow and Katowice, and in a Swedish reference area. Concentrations of Cd, Cu, Fe, Pb, Zn, methyl Hg, ΣDDT, and ΣPCB in tissues of nestlings, were monitored. The birds′ tissue concentrations of the nonessential elements, Cd and Pb, were elevated at the Polish localities, and reflected the degree of environmental contamination. ΣDDT levels were higher in the Polish birds than in the Swedish. Breeding results of the birds were severely affected in southern Poland, and high frequencies of the fledged young showed low Hb.

Breeding Bird Popluations in Grand Teton National Park: Density and Distribution

GTNP (Grand Teton National Park) recently initiated a breeding bird monitoring program, with a view toward assessing population densities of breeding birds and their potential changes, both of residents and neotropical migrants; the 1995 season was the first in which the monitoring protocols of the program were fully instigated. The program goals are the monitoring of both species and densities over a broad range of habitats within the park, with a view to detecting changes over time in these variables, in year-to-year "background" variation and in possible long-term trends. Site selection, mapping and marking, and deployment of various bird census techniques, will be completed and refined over three introductory years, 1995-1997. Thence, it is anticipated that the monitoring program will become permanently established, contributing yearly to an expanding data base on the park's breeding bird populations. This data base, it is believed, will become a useful backup and basis for management decisions, and an increasingly sensitive index from which changes in the park's avifauna, natural or anthropogenic, can be calibrated.

Some new approaches to conservation monitoring of British breeding birds

It is important to monitor bird populations both in their own right and as indicators of the general health of wildlife habitats. The objectives of the British Trust for Ornithology's Integrated Population Monitoring programme relate to breeding bird populations in Britain and Ireland and involve the estimation of demographic parameters as well as assessment of numbers. Current programmes for monitoring bird numbers cover the majority of British species; it would be feasible to monitor most of the rest. A new Breeding Bird Survey has been developed to provide effective coverage of all regions and all major habitats in Britain through random sampling, allowing for the marked geographical variation in volunteer observer density. The final choice of a random sample stratified by observer density (with some professional support in regions with few volunteer observers) was based on comparison with alternative stratifications, using data from a 2‐year pilot study to assess the number of species adequately covered under various alternatives. A method of assessing whether or not targets are being achieved at any time has been developed: it involves looking back through the data at intervals of 1‐year, 4‐year, 16‐year and longer spans. It will be possible to refine this by incorporating environmental and density‐dependent effects into predictive models. The method is illustrated here using Common Birds Census data. We discuss associated problems of statistical inference and of taking decisions under uncertainty. The data provide evidence for large declines in some species, particularly in farmland; the value of birds as general indicators of habitat health is clear. The results of monitoring can be used to illuminate possible causes of problems and to guide both practical steps to ameliorate the problems and research aimed at better understanding the causes. Examples of such research are discussed.

A comparative study of breeding bird populations and associated landscape character, Toruń, Poland

Comparative studies of bird communities inhabiting urban (three sites — two squares and a cemetery), suburban (one site) and forest (two sites) areas were conducted in Toruń, central Poland. Twenty-eight breeding species were recorded in the urban sites (mean 22.7), 37 species in the suburban forest and 45 species in the surrounding forest (mean 35). The total densities of birds in the town were twice as low as those in the forest. The density of shrub-nesters varied from 1.8 pairs per 10 ha in the town to 65.5 pairs per 10 ha in the forest. The density of insectivorous birds decreased with increasing urbanization from 173.4 pairs per 10 ha in the forest to 22.2 pairs per 10 ha in the town. High densities of omnivorous birds were recorded in the town, 38.2 pairs per 10 ha compared with 0.6 pairs per 10 ha in the forest. While 61.1–78.4% of birds inhabiting the urban sites foraged outside their breeding sites, only 39.4–13.8% of the community did so in the suburban and forest areas. Turdus philomelos, Turdus merula, Phylloscopus collybita and Sylvia atricapilla showed signs of adaptation to green areas in the urban zone and bred in high densities in the suburban forest. The study showed that in urban land management the suburban forests should be saved and protected since they create ecological corridors which enable the birds to colonize the urban habitats and maintain their populations there.

Annual Variation in Bird Populations of Mixed Conifer-Northern Hardwood Forests

We examined annual variation in breeding bird populations at sites in northwestern Wisconsin and in the Upper Peninsula of Michigan from 1986 to 1992 to determine (1) the extent to which different bird species vary in abundance over time and (2) whether or not patterns of variation differ when viewed at local and regional spatial scales. Total abundance of long-distance migrants (species that winter in the tropics) declined during the first few years in both states but subsequent increases returned abundance to levels close to those that occurred at the start of the study. Short-distance migrants (species that winter in temperate regions) showed the greatest similarity between states in the extent and direction of variation in abundance among years; abundance reached a low in both states during 1990. Unlike migrant groups, abundance of permanent residents was not correlated between states. Permanent residents declined in abundance from 1987 to 1988 in Michigan, for example, but increased in abundance in Wisconsin. Fluctuations in abundance generally were poorly correlated among groups within a state. Repeated-measures analysis of variance (one-way) revealed that abundances of 13 and 21 (62%) common, long-distance migrants, 13 of 16 (81%) short-distance migrants, and 7 of 9 (78%) permanent residents varied significantly among years in one or both states. Fluctuations in abundance likely occurred in response to events on the breeding grounds. Factors likely to have affected populations include severe drought, particularly during 1987 and 1988, as well as successional changes in habitat. It is unlikely that events on tropical wintering grounds caused population fluctuations observed in neotropical migrants. Two-way ANOV A indicated that patterns of variation differed between the two study regions (significant interaction effects) for a number of species, particularly permanent residents. Results of this study thus ill~trate the importance of considering temporal variation in abundance at more than one spatial scale.

The Effects of Car Traffic on Breeding Bird Populations in Woodland. II. Breeding Dispersal of Male Willow Warblers (Phylloscopus trochilus) in Relation to the Proximity of a Highway

1. In this study the dispersal activity of male willow warblers Phylloscopus trochilus breeding next to a highway carrying heavy traffic was investigated. 2. Breeding dispersal distances of yearling males along the road were larger than at further distances and were in the same order of magnitude as natal dispersal distances (medians being 303 and 515 m, respectively). 3. A simulation of dispersal directions, adjusted for actual landscape features, indicated that breeding dispersal was actively directed away from the road. 4. There appeared to be a relation between dispersal and breeding performance for yearling males, unsuccessful males moving more frequently and further (median 294 m) than successful males (median 120 m)

The Effects of Car Traffic on Breeding Bird Populations in Woodland. I. Evidence of Reduced Habitat Quality for Willow Warblers (Phylloscopus trochilus) Breeding Close to a Highway

This study investigated the effect of a highway with dense traffic on the quality of adjacent habitats for the willow warbler Phylloscopus trochilus. In the zone of 0-200 m from the highway (road zone) the density of territorial males was much lower (2.1 ha −1 ) than in zones with a comparable habitat at a greater distance (3.3 ha −1 ). The lower density in the road zone was due to a low presence of older males. As a consequence, the proportion of yearling males in the road zone was about 50% higher than in the other zones. Yearling males occupied their territories in the road zone later than in the other zones. In the road zone the proportion of successful yearling males was about 50% lower than in the other zones. No difference was observed in the number of nestlings per male

Population sizes and habitat associations of upland breeding birds in the south Pennines, England

The unenclosed uplands of the south Pennines, approximately 725 km 2, were surveyed for upland breeding birds between 12 April and 28 June 1990. The breeding populations of curlew Numenius arquata, golden plover Pluvialis apricaria and merlin Falco columbarius comprised a higher proportion of their national totals than would be expected simply due to the size of the study area, indicating that the south Pennines are of particular importance for these species. Altitude and slope were closely associated with bird distribution. Dunlin Caladris alpina and golden plover were more abundant on high-altitude plateaux, curlew more abundant on low-altitude flat areas, and lapwing Vanellus vanellus, snipe Gallinago gallinago and twite Acanthis flavirostris were more numerous in low-altitude areas with a range of slopes. Associations with vegetation type and structure also varied between species. Red grouse Lagopus lagopus, merlin and short-eared owl Asio flammeus were associated with heather moorland, but no waders or passerines showed any such relationship. Dunlin and golden plover were most strongly associated with blanket bog. Whinchat Saxicola rubetra were closely associated with bracken Pteridum aquilinum cover, and merlin and curlew showed associations with tall heather Calluna vulgaris. The results of the present study are discussed with reference to the importance of the south Pennines breeding bird populations and to the potential effects of habitat change on their distribution and abundance.

Monitoring Breeding Bird Populations in Grand Teton National Park

The central aim of this project is to instigate a permanent program of monitoring landbird species composition and densities in a variety of representative habitats within Grand Teton National Park (GTNP). Habitats range from grassland and sagebrush on the valley floor of Jackson Hole (around 1900 m) through a range of scrub, woodland, and tall foothill forest vegetation types to montane sites of subalpine fir and tundra (ca. 3000 m). The monitoring program will provide data on year-to-year fluctuations in breeding bird species and densities, and eventually on any longer-term changes in the local avifauna, of both resident and migratory species; the data base will further understanding of population variability, local shifts in distribution and abundance, and potentially form a source for management and conservation decisions.

Margrethe-Kog and the Artificial Saltwater Lagoon: Evaluation of a Habitat Restoration Project in the Danish Wadden Sea

Across the Danish–German border in the Wadden Sea, a new dike was completed in 1981, enclosing formerly productive tidal flats and marsh areas which were most important as feeding grounds to breeding and migrant waterbirds. The bird populations responded immediately by a 50% or more reduction in numbers of resting birds and breeding pairs of most species. This paper reviews the management of the enclosed areas, comparing the differences in approach in the Danish and German areas involved.Most importantly, a saline environment was re-established (a Saltwater Lagoon) in parts of the Danish area by actively pumping in water from the Wadden Sea. Despite sometimes drastic fluctuations in environmental conditions in the Lagoon, an infauna of species important in the birds' diet was maintained, and the Lagoon to some extent counteracted the negative effects of the dike construction.The former marsh areas on the Danish side are drained and partly cultivated. In addition, the land areas are separated from the Lagoon by a dike, preventing a saline environment from being maintained outside the designated Saltwater Lagoon. Overall, the land areas in the Danish part are too dry and intensively used to be optimal to the breeding birds.After construction of the dike, the breeding bird populations shifted more towards the German areas. Here, the land-use is much more beneficial to the breeding birds, because no cultivation has taken place, and a generally high water-level in the marsh areas is preserved. Furthermore, in Germany the new dike was placed closer to the original coastline than in Denmark, but a small area of the original foreland remained outside the dike, providing good breeding sites for colonial waterbirds.It is concluded that, due to the creation of the Saltwater Lagoon, the Danish part of the area again sustains waterbirds in numbers of international importance. But an integrated approach to the Nature management of the enclosed areas — combining the solutions adopted for land management in the German part with the technical solution of re-establishing a saline environment behind the dike as in the Danish part — would have rendered a better compensation for the damage caused by the dike construction and related activities.

Summer and winter bird populations associated with five age-classes of aspen forest in Alberta

Summer and winter bird use of aspen forests was studied in west central Alberta. Forest age-classes in the study included 1- and 2-year-old clear-cut areas and.14-, 30-, 60-, and 80-year-old stands. Habitat structure and composition were quantified by a combination of measurement and estimation of variables. Density of the breeding bird population was estimated by territorial mapping. Changes in habitat structure between different age-classes resulted in a successional replacement of bird species. Number of individuals was greatest in 14-year-old stands at 656 territories per 100 ha, probably owing to the presence of remnant snags and of large trees that had survived past fires. The 30-year-old stands supported 312 territories per 100 ha, 60-year-old stands 380 territories, and 80-year-old stands 231 territories, respectively. Recently clear-cut areas supported only 110 territories. Number of species followed the same pattern with 25 in 14-year-old stands, 22 in the 30-year-old stands, 21 in the 60-year-old stands, and 14 in the 80-year-old stands. Recent clearcuts supported 10 species. In winter 13 bird species were recorded in the combined clear-cut, 14-, 30-, and 60-year-old stands. The highest number of species (11) were recorded in the 60-year-old stand during winter but the greatest winter bird density (125 individuals/100 ha) occurred in the 30-year-old stand. Three principal components extracted from the habitat data explained 83.2% of the variance in bird use. The components corresponded to gradients in canopy cover, occurrence of conifers, and shrub density.

Monitoring Migratory Bird Populations in Grand Teton National Park, Northern Rocky Mountains

A scheme for long-term monitoring of breeding land bird populations in a wide variety of habitats representative of the northern Rockies and the Greater Yellowstone Ecosystem (GYE) was initiated in summer 1993. It is projected that the monitoring scheme, when fully established and formalized, will become a routine activity in Grand Teton National Park, where a broad range of representative vegetation types is accessible within close geographic proximity. Sixteen study sites were established within the park in pristine habitat, from the Jackson Hole lowlands to subalpine and alpine sites, from meadow, sagebrush and marshland, through willow scrub, cottonwood and aspen woodlands, to lodgepole pine and spruce-fir forests. Some of the study sites have a long history of research on the breeding birds (see below). Census sites are standardized at 5 ha in size, and mapped in detail (topography, vegetation). The locations and accessibility of the study sites permit all to be regularly and repeatedly censused during the short (6-week) breeding season. Census schedules, timing, and methodological protocols are being established and refined, to provide for strictly controlled inter-site and inter-year comparisons in breeding bird populations, species composition, and densities. In view of the projected benefits to science and resource management of this monitoring scheme, the project hopefully will be continued and the data base further expanded in future years, with a larger range of study sites (24-36).

Breeding Bird Populations in Missouri Ozark Forests with and without Clearcutting

Concern has arisen that forest management practices that create edge (such as clearcutting) are contributing to regional declines in neotropical migrant birds that inhabit forest interiors. Consequently, we studied breeding bird populations in an extensively forested region of southern Missouri to determine if the numbers of breeding birds differed between areas (n = 9) managed by the clearcutting method (CCM), and areas (n = 9) of mature forest with no recent timber harvest or other disturbances (NOHVST). Three forest interior migrants had lower mean densities on CCM sites than NOHVST sites; 3 had greater densities on CCM sites; and densities of 3 others did not differ between treatments. All early successional migrants had greater densities on CCM sites. Numbers of 2 avian nest predators and a brood parasite did not differ on CCM and NOHVST sites. Densities of 9 species differed among regeneration, sapling, and pole-sawtimber habitats on CCM sites.

Breeding-Bird Population Changes Following Right-Of-Way Maintenance Treatments

The effects of herbicide and mechanical vegetation maintenance treatments on breeding-bird populations were compared on electric transmission rights-of-way (ROW) in the Allegheny Mountain and Piedmont Physiographic Provinces in Pennsylvania (hereafter termed the Allegheny ROW and the Piedmont ROW, respectively). Bird density decreased from pre-treatment (June) to post-treatment (August) in 1987 on handcut and mowed plus herbicide-treated ROW areas on both the Allegheny and Piedmont ROW; whereas, bird density increased on basal-, stem-foliage-, and foliagesprayed ROW from pre- to post-treatment. A decrease occurred on the mowed ROW areas only on the Piedmont ROW. Retention of shrubby borders by selective treatment was a major factor in retaining the pre-treatment bird populations in the post-treatment period.

The Breeding Bird Communities of Three Canberra Suburbs

SummaryLenz, M. (1990). The breeding bird communities of three Canberra suburbs. Emu 90, 145–153.The composition and size of the breeding bird populations of three plots with garden city character in Canberra, Australian Capital Territory, were each estimated for one breeding season between 1978 and 1981 using the modified territory mapping method. The number of territories per 10 ha (abundance) were 58.4 (Ainslie). 56.1 (Hackett) and 91.2 (Aranda). Species numbers in the sample areas were 26 (Ainslie, Hackett) and 20 (Aranda). Territories of introduced species, mainly House Sparrow Passer domesticus (44.8–63.5%), Common Starling Sturnus vulgaris (6.8–23.0%) and Blackbird Turdus merula (1.27.6%), comprised between 71–79% of the total number of territories. The only dominant native bird species was the Silvereye Zosterops lateralis (5.9–10.3%). 40–69% of all bird species ranked as rare (each < 1 % of the total population). The abundances of native bird species, excluding the Silvereye, were 5.9 T/10 ha in Ainslie, 8.5 T/10 ha in Hackett and 18.9 T/10 ha in Aranda, probably reflecting the extent of native trees and shrubs in streets and gardens. In Ainslie, the vegetation was composed largely of exotic species. In Hackett, native trees (eucalypts) were more common but distributed unevenly. In Aranda, native vegetation dominated, many trees had been retained from the original woodland. Aranda supported a significantly higher population of exotic birds (65 T/10 ha) than Ainslie (46.5 T/10 ha) and Hackett (44.2 T/10 ha); many cavities in the original eucalypts provided House Sparrows and Common Starlings with more nest sites than were available in the other plots.

Scotlands threatened mires and mosses: Policies to protect the peatlands of caithness and sutherland

Summary Scottish peatlands have suffered loss and damage for centuries through cutting for fuel and agricultural and forestry practices. The ombrogenous blanket mires of Caithness and Sutherland (the ‘Flow Country’) are of international importance for the range and quality of their peatland types and vegetation, and their breeding bird populations. Loss of this habitat in the last decade, due to rapid expansion of forestry, caused great concern which was expressed by voluntary and statutory nature conservation organizations and the national media. Government at both national and local levels responded with changes in forestry policies, protection of large areas of peatland and by a land-use strategy which divides the area into four forestry policy zones.

Nest Predation and Brood Parasitism of Tallgrass Prairie Birds

Rates of nest predation and brood parasitism on 5 bird species nesting in fragments of tallgrass prairies in Minnesota were affected by the size of the prairie fragment containing the nest, the distance from the nest to a wooded edge, and the number of growing seasons since the vegetation around the nest was last burned. Rates of nest predation for 5 species were lower (P < 0.10 in each case) for nests on large (-130 ha) fragments, in areas far (?45 m) from a wooded edge, and in vegetation that was recently burned (s3 yr). Rates of brood parasitism were lower (P < 0.10 in each case) far from a wooded edge. Prairie management to maximize nest productivity should provide large, regularly burned prairies with no nearby wooded edges. J. WILDL. MANAGE. 54(1):106-111 More than 99% of the presettlement tallgrass prairie in Minnesota has been converted to agriculture and other uses. Remnant tracts of prairie are usually small, isolated parcels surrounded by habitat unsuitable for most prairie birds. Many of the remaining prairie fragments contain invading tree species, such as aspen (Populus tremuloides) and willow (Salix spp.), and/ or cottonwood (Populus deltoides) shelterbelts. Natural fires, once common occurrences in the tallgrass prairie (Daubenmire 1968), are suppressed, but prescribed burning is now a major management activity on native prairies. Several animals that depredate or parasitize nests of prairie birds have recently increased in abundance in western Minnesota. For example, raccoons (Procyon lotor), nest predators once limited to southeastern Minnesota, have expanded their range into the prairie region and are now common (Hazard 1982). Densities of red fox (Vulpes vulpes) have increased due to changes in agricultural practices and the reductions of other canids (Johnson and Sergeant 1977). In addition, brown-headed cowbirds (Molothrus ater), an obligate brood parasite, have greatly increased in abundance since 1900 (Brittingham and Temple 1983). Currently, most management of prairie fragments is undertaken to perpetuate native plant communities, but little is known about how vegetation management affects breeding bird populations on prairies. Consequently, we studied the effects of nest predation and brood parasitism on the productivity of birds nesting in managed tallgrass prairies in western Minne-

Breeding bird populations of farmland in mid-west Ireland in 1987

The breeding bird populations of 5 farmland plots in mid-west Ireland were censused during 1987. The results show that Wren, Robin, Blackbird, Dunnock and Chaffinch are the most common species, with the Wren being numerically dominant in all plots. The Wren and Robin form a much greater proportion of the farmland bird populations than in Britain. Reasons for this difference are discussed.

The effect of nestboxes on breeding populations of birds in broadleaved temperate woodlands

Removal of nestboxes from a semi‐mature, broadleaved woodland caused a decrease in the number of breeding pairs of Great Tits, but did not significantly reduce breeding densities of Blue Tits. Breeding densities of warblers were unaffected by changes in the population of Great Tits. In the absence of nestboxes, intraspecific competition for natural nestholes was more intense amongst Great Tits than Blue Tits. Great Tits tended to occupy larger holes on or near the trunk, while Blue Tits used smaller holes on side branches. Nesting success for both species was lower in natural cavities than nestboxes, due to a higher percentage of total nest failures. The reintroduction of nestboxes did not produce an immediate rise in the breeding population of Great Tits; possible reasons for this are discussed.

The effect of nestboxes on breeding populations of birds in broadleaved temperate woodlands

Removal of nestboxes from a semi‐mature, broadleaved woodland caused a decrease in the number of breeding pairs of Great Tits, but did not significantly reduce breeding densities of Blue Tits. Breeding densities of warblers were unaffected by changes in the population of Great Tits. In the absence of nestboxes, intraspecific competition for natural nestholes was more intense amongst Great Tits than Blue Tits. Great Tits tended to occupy larger holes on or near the trunk, while Blue Tits used smaller holes on side branches. Nesting success for both species was lower in natural cavities than nestboxes, due to a higher percentage of total nest failures. The reintroduction of nestboxes did not produce an immediate rise in the breeding population of Great Tits; possible reasons for this are discussed.