Ground-nesting Species Research Articles

Large-scale land use change may explain bird species declines in semi-natural areas: the case of Black Grouse population collapse in Lower Saxony, Germany

Farmland birds in Central Europe have been heavily declining in past decades. Among them are many ground-nesting species, adapted to semi-natural but secondary habitats. A vivid example is the Black Grouse (Tetrao tetrix) in the lowlands of north-western Germany, the Netherlands and Denmark, where the species′ populations experienced dramatic declines between the 1950s and 1970s. One explanation for these ubiquitous population declines might be large-scale changes in agricultural land use and land cover. We investigated several agricultural indices at three hierarchic administrative scales in parts of the federal state Lower Saxony, Germany, and related changes in these indicators with the Black Grouse declines. Land cover proportions remained relatively stable whereas indices of agricultural intensification heavily increased from 1952 to 1973. Multiple regression showed that change in farmland area was the best predictor of the trends across scales. Correlates of Black Grouse abundance were moor at the medium scale and pasture cover and fallow land at the smallest scale. Our results support the hypothesis that Black Grouse population dynamics in the lowlands of Central Europe were affected by land use changes. They show that Black Grouse populations in Central Europe were dependent upon extensive farming and may provide additional explanation where underlying factors on the habitat scale cannot fully explain the declines.

Population genetics of Formica ants

Enzyme gene variability was studied in European populations of 13 Formica ant species. Average gene diversity within nests ranged in different species from 0 to 0.047 and within populations from 0 to 0.078, the averages being 0.015 and 0.043, respectively. The results are consistent with earlier studies and theoretical models, which predict reduced genic variation in haplodiploid species. The evolutionary strategies of aculeate Hymenoptera may deviate the genetic structure of populations to the same direction as haplodiploidy, either by stabilizing environmental conditions or splitting the population into small groups with increasing ability to inbreeding. The results indicate genotype-environment interaction, as the average gene diversity was lower in nests and populations of mound-building species with stable and permanent nests, than in ground-nesting species. This was partly due to the social structure of the populations, as such a difference was not observed among the monogynous species. The amount of variation increased with increasing degree of polygyny and polycaly among the ground-nesting species, but not in the mound-building species. Geographic differences between conspecific populations were small. Differentiation was remarkable only between disjunct populations of F. aquilonia from Finland and Scotland.

Habitat relationships of diurnal raptors at local and landscape scales in southern temperate grasslands of Argentina

We evaluated the relationship between an assemblage of diurnal raptors and local-and landscape-scale habitat variables in the eastern portion of South America's temperate grasslands in Argentina (37°32'-37°45'S, 57°19'-57°26'W). The landscape is a mosaic of agroecosystems and natural grasslands. Raptor species were sampled using fixed-distance point-counts, from October 2004 to February 2005. We used generalised additive models to analyse the relationship between raptor occurrence or abundance and environmental predictors at two spatial scales: local (at plot level) and landscape (areas of 25 and 100 km2 around the survey points). At local scales we measured vegetation height and percentage cover. Landscape-scale variables included percentage of each habitat type, landscape diversity, and fractal dimension. Higher values of species richness were recorded in landscapes with a complex matrix of disturbed and undisturbed plots. The abundance of Chimango Caracara (Milvago chimango) was positively associated with roads, sites with a complex matrix of disturbed and undisturbed plots, and high levels of forest cover. The presence of Long-winged Harrier (Circus buffoni) increased in landscapes dominated by natural habitats, mainly natural grasslands. The presence of Southern Crested Caracara (Caracara plancus) increased mostly in plots with high amounts of short grass cover and away from roads. Based on our results, we suggest that maintenance patches of natural grassland is essential for the preservation of ground-nesting species, and preservation of habitat diversity would ensure that most of the raptor species in the assemblage had their ecological requirements met.

Livestock grazing, plateau pikas and the conservation of avian biodiversity on the Tibetan plateau

On the Qinghai–Tibet plateau increased livestock numbers have resulted in degradation of the grasslands with potential impacts on native biodiversity. Concurrently, perceived increases in populations of native small mammals such as plateau pikas ( Ochotona curzoniae) have led to poisoning programs, with uncertain impacts on species such as ground-nesting birds. We explored the relationships between the local seasonal abundance of small birds and (1) the density of pika burrows; (2) livestock grazing practices; and (3) local poisoning of pikas. Around Naqu prefecture, central Tibet, we used a nested experimental design to collect data from areas rested from grazing over summer, nearby areas with year-round grazing and areas subjected to pika poisoning. Additional data were collected from a site where grazing had not occurred for at least 4 years prior to the study. Poisoning pikas in spring had no detectable effect on the local abundance of birds the following autumn. However, two ground-nesting species, white-rumped and rufous-necked snowfinches, showed positive associations with the density of pika burrows, indicating that long-term pika poisoning could reduce the density of these species by reducing the density of pika burrows. Rufous-necked snowfinches and non ground-nesting species including horned larks and common hoopoes showed positive responses to reduced grazing pressure from livestock, particularly in the long-rested site, indicating current grazing levels could be having a negative impact on these species. Conservation of small passerine biodiversity in this system will require changed management practices for livestock and pikas that consider the complex three-way interaction between livestock grazing, pikas and small birds.

Predation on artificial ground nests in birch forests fragmented by spruce plantations

Spruce planting (Picea abies) in coastal birch forests (Betula pubescens) of northern Norway could influence ground-nesting species such as willow ptarmigan (Lagopus lagopus) and black grouse (Tetrao tetrix). Predator-specific predation rates on baited trackboards were therefore studied in 3 successional edge gradients: birch forest adjacent to (1) closed spruce plantations, (2) open spruce plantations, and (3) clearings. We also examined the influence of 2 types of landscapelevel variables on predation rates: the distance from sampling location to the nearest roads and buildings and the land use composition within a 1-km radius of the sample. Predation rates were dominated by 2 generalist species: red fox (Vulpes vulpes) (19.2%) and hooded crow (Corvus corone cornix) (7.5%). Predation appears dependent on the successional stage of spruce plantations, with areas near clearings (63.5%) and open spruce plantations (59.8%) experiencing higher predation pressures than closed spruce plantations (45.3%). However, predation rates were highly variable among landscape blocks. Neither landscape nor vegetation variables could explain this block-level variation. We discuss alternative mechanisms that could explain differences between landscape blocks, but further studies are needed to understand the spatial heterogeneity of predators at larger scales.

The influence of developmental environment on the evolution of olfactory foraging behaviour in procellariiform seabirds

The evolutionary origins of foraging behaviour by procellariiform seabirds (petrels, albatrosses and shearwaters) are poorly understood. Moreover, proximate factors affecting foraging ecology, such as the influence of environment on the development of sensory systems, have yet to be addressed. Here, we apply comparative methods based on current procellariiform phylogenies to identify associations between sensory modalities and the developmental environment that may underlie the evolution of complex foraging behaviour. We postulate that, for burrow-nesting species, smell is likely to dominate the sensory world of the developing chick. Alternatively, for ground-nesting species, chicks receive exposure to a range of visual, auditory and olfactory cues. We employ maximum likelihood to test models of correlated trait evolution between nesting habit and olfactory foraging style and to reconstruct the ancestral states of these characters when coded as binary states. Our results suggest that nesting behaviour has evolved in conjunction with foraging style. Based on this analysis, we propose that nesting on the surface was a life-history innovation that opened up a new developmental environment with profound effects on the foraging ecology of procellariiform seabirds.

Bait-delivered pimozide causes precocious embryo implantation in mink: a fertility control option for the exotic stoat?

Stoats (Mustela erminea), an exotic pest in New Zealand, threaten the conservation of several ground-nesting bird species and broad-scale methods for their control are sought. Females are seasonally monestrous, show a 9-month period of obligatory diapause and usually do not breed more than once in their lives. A bait-delivered agent that terminates diapause and results in a non-viable embryo may have a significant impact on their reproductive success. Prolactin (PRL) is hypothesised to be the only gonadotrophin required for renewal of luteal activity and blastocyst implantation in some mustelids. We investigated the effects of bait-delivered dopamine (DA) antagonists (which stimulate the release of PRL) using a mink model (Mustela vison), a species that maintains a short period of diapause. A bait dose of 0.8 mg kg(-1) of pimozide was more effective in elevating PRL levels than equivalent doses of fluphenazine, sulpiride (P < 0.01) or haloperidol (P < 0.05). Bait doses of 1.6 mg kg(-1) pimozide given at Days 0, 3, 9 and 11 after mating caused a significant reduction in the length of pregnancy compared with a positive control and placebo (46 days v. 51 days), indicating early termination of diapause (P < 0.01). Pimozide doses caused higher elevations in PRL concentration relative to the oral placebo by Day 12, but mean PRL levels fell below all other groups by Day 18. A borderline significant increase in progesterone (P4) secretion compared with the oral placebo was detected at Day 18. These results suggest that bait-delivered pimozide can elevate PRL outside of the normal breeding season and doses of 1.6 mg kg(-1) are effective in terminating embryonic diapause in mink. The implications and limitations of these data are discussed with reference to the use of bait-delivered DA antagonists as a possible means to affect the reproductive success of wild stoats.

Bird–Vegetation Relationships in Southeastern British Columbia

To produce better habitat models, we analyzed a 1977 breeding bird data set with recently developed techniques. Our generalized linear models for specific bird species produced precise descriptions of bird–vegetation relationships, using visually obvious habitat features (e.g., grass, broad-leaved shrubs, and conifers of differing heights). This was, in general, confirmed by canonical correspondence analysis, which related the entire bird community to the vegetation across the successional stages. Nevertheless, our analyses produced some results that contradicted our expectations; ground-nesting species negatively associated with bunch grasses (species that grow in clumps within the Agropyron, Festuca, and Stipa genera), and cavity-nesting species negatively associated with stumps and snags. We speculate that those contrary relationships resulted from nest sites not being a limiting resource. We conclude that visually obvious vegetation features are sufficient to describe most breeding bird–habitat relationships. Further, appropriate landscape management for bird biodiversity requires that all successional stages are present.

Impacts of Argentine ants on avian nesting success

Biological invasions can have severe and widespread impacts on ecological communities. A few species of ants have become particularly damaging invaders but quantitative data of their impacts on many taxa is still lacking. We provide experimental evidence using artificial nests baited with quail eggs that the invasive Argentine ant (Linepithema humile) can be a significant avian nest predator – Argentine ants recruited to more nests and in higher abundance than the native ant species they displace. However, at a site invaded by Argentine ants, we monitored over 400 nests of a ground-nesting species, the Dark-eyed Junco (Junco hyemalis), and found that less than 2% of nests failed as a result of Argentine ant predation/infestation. A review of the literature also suggests that Argentine ants may not be a serious threat to bird nests relative to other predators or parasites. However, invasive ants with the capability of overwhelming prey though stinging (specifically the red-imported fire ant, Solenopsis invicta), may have a higher impact on avian nesting success.

Grazing animals as habitat engineers for ground-nesting birds – a review of the issues

Habitats associated with livestock production systems are important in terms of avian biodiversity in the UK and across Europe. Livestock play an integral role in structuring grassland habitats, which in turn affects their suitability for different ground-nesting bird species. Such habitat engineering is driven mainly by the effect of grazing on plant species composition and vegetation structure. However, ground-nesting birds are also negatively affected by the presence of grazing animals since livestock destroy nests mainly through trampling.

Variation in nest predation among arid-zone birds

I examined the nesting habits and success of 11 co-existing species in an arid, sub-tropical habitat in South Africa. Nesting success ranged from 3.5% to 75.4% among species, with predation by mammals and snakes accounting for 94% of nest losses. Differences in predator avoidance behaviour (deserting the nest vs sitting tight) may explain markedly different daily nest predation risk experienced by the Double-banded Courser Rhinoptilus africanus (0.5%) and Namaqua Sandgrouse Pterocles namaqua (9.2%). Nest predation was inversely related to nest density, but this reverse density dependence may reflect a seasonal effect, as predation decreased as the breeding season progressed from spring to mid-summer. Overall, daily egg predation rates were higher than daily nestling predation rates among nine altricial species, contrary to the widely-held view that increased activity at the nest during the nestling period increases predation risk. The prediction of higher daily nest predation rates on ground-nesting species than on shrub/tree-nesting species in an open habitat was supported. Among ground-nesting species, territorial residents suffered significantly lower daily nest predation rates than nomads, suggesting that residents may use experience of local predator activity to place their nests in safer sites.

The occurrence of runt eggs in waterfowl clutches

Eggs that are abnormally small are called runt eggs, and they occur in clutches across a wide variety of bird species. We surveyed waterfowl researchers to determine the natural frequency of occurrence of runt eggs in wild nesting ducks, geese, and swans. Of 551,632 eggs examined, 215 were runts, yielding a frequency of 0.039%. They occurred at about four times this frequency (0.156% in 21,832 eggs) in a museum oological collection. Runt eggs were not significantly more common within any taxonomic group among wild waterfowl, and their occurrence was not related to the mean clutch size of a species or to whether waterfowl exhibited regular conspecific nest parasitism. Cavity-nesting waterfowl had lower incidences of runt eggs than ground-nesting species. Our results represent the largest examination of the occurrence of this size anomaly in eggs of wild birds, and are consistent with the hypothesis that runt eggs result from a temporary impairment of the reproductive tract. This may explain why runt eggs occur in all bird species studied.

BIRD COMMUNITIES IN THINNED VERSUS UNTHINNED SIERRAN MIXED CONIFER STANDS

We used point counts and nest monitoring to compare avian community composition and nesting success in thinned and unthinned stands of commercially managed Sierran mixed conifer forest. We conducted point counts and monitored 537 active nests of 37 species on 10 study plots during three consecutive breeding seasons in the northern Sierra Nevada. All 10 study plots had experienced a similar long term man- agement history that included fire suppression and single-tree selection logging, but five of the plots also un- derwent a protocol of combined commercial and biomass thinning 5-8 years prior to the beginning of the study. Pooling species by nest substrate, we found that detections of ground-nesting bird species were similar on thinned and unthinned plots, but we detected canopy-, cavity-, and especially shrub-nesting species much more frequently on the thinned plots. Nest success rates were not statistically different between thinned and unthinned plots for ground-, shrub-, canopy-, or cavity-nesting species. Thinned stands were characterized by significantly less canopy cover, significantly lower density of small and medium conifers, and significantly greater understory cover and deer brush (Ceanothus integerrimus) cover than the unthinned stands. We surmise that the thinning protocol stimulated vigorous shrub growth, and conclude that forest conditions associated with a relatively open canopy and a well-developed shrub understory are highly beneficial to numerous breeding bird species in the Sierran mixed conifer community, including many species that may not nest or forage in the understory. Forest thinning that promotes vigorous shrub growth may correlate with an increased abundance of nesting birds, at least within stands affected by historical fire suppression and single-tree selection logging. Received 1 October 2002, accepted 5 March 2003. Logging practices and human-altered fire regimes have changed forest structure and composition across much of the Sierra Nevada since the mid-Nineteenth Century (Franklin and Fites-Kaufmann 1996, Gruell 2001). Tim- ber harvest practices and fire suppression throughout much of the region generally have reduced the frequency of low intensity fires, reduced the number of large trees, increased the density of smaller trees, and possibly re- duced the extent of shrub cover (Weaver 1974,

Influence of insecticide treatments on ant-hemiptera associations in tropical plantations.

In this survey conducted in southern Cameroon, we compared ant-Hemiptera associations on plantations treated with insecticides, on plantations 2 years after insecticide treatments ceased, and on control lots that never received insecticide treatments. By eliminating arboreal-nesting ants, insecticides favored the presence of "ecologically dominant" ground-nesting, arboreal-foraging species that occupied the tree crowns. The reinstallation of arboreal ants was slow as 2 yr after insecticide treatment ceased differences with the control lots were significant. This intermediary period also illustrated that arboreal ants can found and develop colonies on trees occupied by ground-nesting species. Certain arboreal species were more frequent during this intermediary period than on the control lots, showing that the period of installation in the trees was followed by competition between arboreal ants. We confirm that ground-nesting ants tend a wide range of hemipteran families, including well known agricultural pests, whereas arboreal ants, particularly dominant species, were mostly associated with Coccidae and Stictococcidae that do not pose problems to the supporting trees. A tree effect was also noted for both ant and hemipteran distribution. We concluded that because of insecticide use, ground-nesting ants pose problems through their associated Hemiptera. On the contrary, dominant arboreal ants, strong predators, benefit their supporting trees by excluding ground-nesting species and tending mostly nonpest Hemiptera. Nevertheless, certain of them, carpenter species or species likely to tend Pseudococcidae, have to be eliminated through integrated management.

Oocytes, Eggs, and Ovarioles of Some Long-Tongued Bees (Hymenoptera: Apoidea)

NOTE Appendix: Parammobatodes rozeni, a New Bee Species from Israel, by Maximilian Schwarz3We present here new information regarding the number of ovarioles and the number and size of mature oocytes of certain bee taxa collected on a field trip in Turkey in June and July 2001. This information is augmented with similar data concerning taxa related at the tribal level to those that we found in Turkey. The mature oocytes/eggs of all taxa listed below are described and most are illustrated by photographs, scanning electron micrographs, and/or line drawings, and comparisons are made with previously published descriptions.These taxa, arranged by family, subfamily, and tribe, are as follows: MEGACHILIDAE: Megachilinae: Dioxyini: Dioxys cincta (Jurine), Dioxys pacificus Cockerell. APIDAE: Xylocopinae: Xylocopini: Xylocopa (Proxylocopa) olivieri Lepeletier; Nomadinae: Ammobatoidini: Holcopasites insoletus (Linsley), Holcopasites tegularis Hurd and Linsley; Nomadinae: Biastini: Biastes brevicornis (Panzer); Nomadinae: Ammobatini: Ammobates carinatus Morawitz, Parammobatodes rozeni Schwarz, Oreopasites (Oreopasites) favreauae Rozen, Oreopasites (Oreopasites) vanduzeei Cockerell, O. (Perditopasites) barbarae Rozen, O. (P.) linsleyi Rozen, “Parammobatodes” orientana (Warnke), Pasites maculatus Jurine, Sphecodopsis (Pseudodichroa) capensis (Friese), S. (P.) fumipennis (Bischoff); Apinae: Melectini: Melecta albifrons albovaria Erichson, Melecta species, Thyreomelecta kirghisia Rightmyer and Engel, Thyreus lieftincki Rozen, Xeromelecta californica (Cresson).The mature oocyte of Xylocopa (Proxylocopa) olivieri, a ground-nesting species, is found to be large relative to the body size of the female but somewhat smaller than the “giant” eggs of wood-nesting Xylocopa, as classified by Iwata and Sakagami (1966. Gigantism and dwarfism in bee eggs in relation to the mode of life, with notes on the number of ovarioles. Japanese Journal of Ecology 16: 4–16). Egg deposition habits of some cleptoparasitic taxa are discussed. In addition to smaller size relative to body size, eggs of cleptoparasitic bees show great variation in micropylar structure, dimensions, and chorionic ornamentation, thickness, and patterning, compared with eggs of nonparasitic bees.An appendix by Maximilian Schwarz describes and names Parammobatodes rozeni, new species, from Israel.

Variation in a sparrow's reproductive success with rainfall: food and predator-mediated processes.

From 1997 to 1999, we monitored the reproductive success of individual rufous-crowned sparrows (Aimophila ruficeps) in coastal sage scrub habitat of southern California, USA. Annual reproductive output of this ground-nesting species varied strongly with annual variation in rainfall, attributed to the El Niño-Southern Oscillation. Birds fledged 3.0 young per breeding pair in 1997, when rainfall was near the long-term mean, 5.1 offspring per pair in 1998, a wet El Niño year, and 0.8 fledglings per pair in 1999, a dry La Niña year. Variation in many components of reproductive output was consistent with the hypothesis that food availability was positively correlated with rainfall. However, the factor most responsible for the high reproductive output in 1998 was low early season nest predation which, combined with favorable nesting conditions, enabled more pairs to multiple-brood. Cool, rainy El Niño conditions may have altered the activity of snakes, the main predator of these nests, in the early season of 1998. Overall, more of the annual variation in fecundity was attributable to variation in within-season components of reproductive output (mean number of nests fledged per pair) than to within-nest components (mean brood size). Annual variation in rufous-crowned sparrow fecundity appears to be driven primarily by food resource-mediated processes in La Niña years and by predator-mediated processes in El Niño years.

SPECIES-SPECIFIC EDGE EFFECTS ON NEST SUCCESS AND BREEDING BIRD DENSITY IN A FORESTED LANDSCAPE

Using natural nests of eight bird species, we provide one of the first multi- species tests for edge effects on reproductive success in a forested landscape. Our primary objective was to assess whether distance to the edge of recent clearcuts was related to nesting success in intact northern hardwood forests. Estimated nest success was generally lower for the two ground-nesting species than for the six canopy-nesting species. Brood parasitism was <3% for species which typically accept eggs of the Brown-headed Cowbird (Molothrus ater), and nest predation was the most common cause of nest failure. Probability of nest failure was influenced by distance to forest edge for the ground-nesting Hermit Thrush (Catharus guttatus) and Ovenbird (Seiurus aurocapillus), but not for six canopy- nesting species. For the Hermit Thrush and Ovenbird, nest success relative to decreasing distance to the edge was reduced during the nestling stage, but not the incubation stage. Nest density appeared to be higher in forest zones near the clearcut edge for ground-nesting and for several canopy-nesting species. Our data suggest that the effect of proximity to edge on nest success for ground-nesting species may penetrate 300 m into intact forest, while the effect of proximity to edge on nest density may penetrate farther. These data suggest that the creation of openings in forested landscapes reduces nest success and in- creases nest density for some species of migratory birds in a zone adjacent to the opening. This pattern supports the notion that ecological traps may exist for ground-nesting birds in areas near recently created forest openings. Because areas of contiguous forest (e.g., publicly owned forest) in the Upper Great Lakes remain relatively intact, they may serve as source habitat for regional songbird metapopulations. ~ and ~~~~l~ 1983, paton 1994, ~i~~ ~ i ~ ~

The effects of stand age on avian communities in aspen-dominated forests of central Saskatchewan, Canada

Timber harvest projections for aspen-dominated forests in the prairie region of Canada include a truncation of the current age distribution, whereby old stands of fire origin will become rarer on the landscape, while young, post-harvest stands will increase in abundance. To determine the effects this harvesting strategy might have on communities of breeding forest birds, we conducted point counts in young forests regenerated from clear-cutting (15–25 years), and mature (50–60 years), and old (80–110 years) forests regenerated from fire. Avian species richness was highest in old stands at the point-count station, forest stand, and landscape level. Increased species richness with forest age was associated with increases in the relative abundance of canopy- and cavity-nesting species. At local scales (station and stand), species richness of ground- and shrub-nesting birds was similar among forest age-classes. However, as determined by rarefaction analyses appropriate at the landscape scale, ground-nesting species were more common in young and old forests, while shrub-nesting species were more common in young and mature forests. Density of deciduous shrubs was an important factor influencing the abundance of species like American redstart, Canada warbler, and chestnut-sided warbler. An increase in conifer in old stands resulted in greater use by conifer- or mixedwood associated species such as bay-breasted warbler, magnolia warbler, and ruby-crowned kinglet. Our data indicate that vegetation and structural characteristics such as shrub density should be considered when prescribing sustainable forestry objectives.

INVESTIGATOR EFFECTS ON THE NESTING SUCCESS OF ARID-ZONE BIRDS

Abstract We examined whether regular researcher visits affected egg hatchability or nest predation for three ground-nesting bird species that incur high levels of nest predation, primarily by small mammals. Frequently visited finch-lark (Eremopterix verticalis and E. australis) nests suffered similar predation to nests visited infrequently, suggesting that regular visits had no additive effects on nest survival. A comparison of finch-lark nests visited for the second time either one or two days after the first visit found that predation during the first 24 h (7.4%) was lower than predation during the second 24-h period (9.9%), suggesting that the act of visiting a nest did not increase the risk of predation. Daily predation rates on Namaqua Sandgrouse (Pterocles namaqua) and finch-lark nests showed no observable trend with an increasing number of visits over time, indicating that frequent visits had no cumulative effect on predation probabilities. Nests of both Grey-backed Finch-lark (E. verticalis) and B...

Occurrence of breeding bird species in urban parks: Effects of park structure and broad-scale variables

Occurrences of breeding bird species in 54 urban parks were investigated in the city of Oulu in northern Finland. Park area, human activity, habitat, and landscape structure within a 9-ha square surrounding the study park were related to the bird species richness and occurrence of individual bird species. A total of 22 species was observed. The area of the park explained 39% of the variance of species richness. Seven species (wheatear [Oenanthe oenanthe], common rosefinch [Carpodacus erythrinus], garden warbler [Sylvia borin], lesser whitethroat [Sylvia curruca], linnet [Acanthis cannabina], redpoll [Carduelis flammea], and yellowhammer [Emberiza citrinella]) were not detected in parks of >0.75 ha. Species with lower area demands occurred closer to the town center than species with greater area requirements. Ground-nesting species were poor colonizers of urban parks, whereas high numbers of nest boxes in urban parks attracted many cavity-nesting species. The willow warbler (Phylloscopus trochilus) and the magpie (Pica pica) bred more often in unmanaged than in managed parks, probably because of the greater vegetation cover in unmanaged parks. Park structure variables were entered into models for 7 of the 12 most common bird species, whereas broad scale variables were entered into models for 6 of the 12 species. The number of adjacent buildings had a negative affect on three bird species (the willow warbler, hooded crow [Corvus corone cornix], and spotted flycatcher [Muscicapa striata]). The occurrence of breeding species in urban parks depends on the size of the park, park structure, and landscape structure outside the park.