Nesting ecology and conservation of shrubland birds in a fragmented urbanized landscape in northeastern Illinois

shrubland birds;nesting ecology;landscape ecology;depredation

Secker, Heather ; Ward ; Michael P.

关键词: shrubland birds;    nesting ecology;    landscape ecology;    depredation;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/73061/Heather_Secker.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Current declines in shrubland bird populations and habitats in eastern North America highlight the importance of understanding the nesting ecology of shrubland birds. The majority of the literature on shrubland birds has focused on communities in regenerating forest areas following silvicultural practices. Little information exists regarding nesting ecology and success of shrubland birds in fragmented patches in urbanized areas in regenerating agricultural fields. Nesting success/failure may co-vary with factors such as bird species, predator type, weather, microhabitat conditions at the nest, and landscape factors. Although many studies consider avian species-specific differences, most group types of depredation/failure rather than linking specific predators to nesting success/failure and then comparing levels of success/failure to other variables. The purpose of this study was to combine nest observations, video camera technology, and historical point count data to examine the influence of vegetative factors, landscape factors, and types of nest failure/depredation on habitat use and nesting success of shrubland birds in regenerating agricultural fields in an urban/suburban landscape matrix near Chicago, Illinois. A total of 53 active nests of 12 species were monitored at two sites including shrubland patches of various sizes during late May-August 2010. Approximately 39% of nests failed, and the mean percentage of young fledged (of all known eggs/young) was 52%. Many nests failed partially at different times during the nesting cycle. Depredation and weather (particularly high winds associated with thunderstorms) contributed to the most failures, although other factors such as destruction by House Wrens (Troglodytes aedon) and/or other bird species, and abandonment due to Brown-headed Cowbird (Molothrus ater) parasitism were also documented. All nests experiencing Brown-headed Cowbird parasitism failed (n=5). Red-winged Blackbird (Agelaius phoeniceus) was one of the most successful species; Willow Flycatcher (Empidonax traillii) was one of the least successful, and failure rates were higher than some reported from rural, agricultural areas in Illinois. Species-specific variation existed in the types of trees and shrubs used for nesting purposes; some species utilized Gray Dogwood (Cornus racemosa) exclusively. Percent vegetative cover above nest, area of patch, and distance from the nearest shrubland patch edge did not influence success. Fledgling success increased with increasing nest height, distance from roads, and in some cases, distance from trails. An above average percentage of nests located in trees/shrubs with thorns fledged. No significant relationship existed between patch area and species richness or the number of species confirmed breeding, but larger patches did support higher numbers of individuals. Elucidating how landscape and vegetative factors, depredation ecology, avian behavior, Brown-headed Cowbird parasitism, and weather affect nest success/failure (particularly as increased urban sprawl causes habitat loss and degradation and climate change contributes to weather-related variation) can benefit conservation and management practices for shrubland birds, including species experiencing declining population trends.