Do natural areas in urban landscapes support successful reproduction by a group of conservation priority birds?

Abstract

If conservation priority birds are to persist in an increasingly anthropogenically altered world, suitable habitat must be created or preserved in potentially unsuitable landscapes. While natural areas in urban environments may provide habitat for declining groups of birds, little is known about effects of urbanization on the reproductive success of birds, such as grassland birds, that are typically thought to be associated with more rural landscapes. While typical conservation efforts have focused on conserving large patches of grassland in landscapes containing minimal amounts of woody vegetation and development, the assumption that habitat located in developed landscapes is of poor quality has not been tested and may wrongly devalue grasslands located in an urban matrix. To examine the influence of development on habitat quality for grassland birds, we studied grassland bird nest predation and brood parasitism in patches of varying size along an urbanization gradient in northeastern Illinois. Because nest predation is the primary cause of reproductive failure and a potentially limiting factor for grassland bird populations, we used miniature video cameras to identify predators at a subset of nests. From 2012 to 2013, we monitored 432 nests of 16 grassland bird species. Nest predation rates decreased with urbanization in the landscape as did probability of brood parasitism. We filmed 44 nests and documented 19 predation events. We found that coyotes Canis latrans, white-tailed deer Odocoileus virginianus and thirteen-lined ground squirrels Ictidomys tridecemlineatus were important nest predators in our study system. Contrary to prior assumptions, our results suggest that grasslands located in urban landscapes may provide habitat of equal or greater quality than many rural grasslands.

Effects of fragmentation and landscape matrix on the nesting success of grassland birds in the Pampas grasslands of Argentina

“…The effects of urbanization on nesting success of grassland birds have been little studied. However, our results agree with those recently described by Buxton and Benson (), who found that nests of grassland birds (mostly of Red‐winged Blackbird Agelaius phoeniceus ) in urban landscapes had lower nest predation rates than nests in more rural landscapes (but see Grandmaison & Niemi ). Rodewald et al .…”

“…Mermoz and Reboreda () found that the rate of brood parasitism of Marshbirds nesting mostly in patches of thistles Cynara cardunculus growing in field margins along secondary unpaved roads was 65.4%, a value similar to that found in this study (agro‐patches: 72.2% and urban‐patches: 58.8%). Also for grassland birds, Buxton and Benson () observed that brood parasitism by Brown‐headed Cowbirds Molothrus ater was greater in rural areas than in urban areas, indicating that this pattern may be similar irrespective of grassland‐host species, and that it relates mainly to the abundance of brood parasites, as in both study areas the abundance of cowbirds decreased with urbanization in the landscape (Buxton & Benson , Pretelli ). Higher brood parasitism and productivity of parasite nestlings in agro‐patches would generate a system that promotes a negative feedback process whereby parasite populations benefit to the detriment of native hosts.…”

“…Recently, Buxton and Benson () found that nests in urban landscapes had lower nest predation rates than nests in more rural landscapes, and that brood parasitism was also less frequent in more urbanized landscapes. Accordingly, evidence for matrix effects on grassland habitats has been equivocal (Johnson , Lahti ).…”

Mixed effects of urbanization on density, nest survival, and nestling corticosterone of a generalist passerine

“…Consequently, using predator activity or abundance as a cue of habitat quality may cause birds to incorrectly devalue habitats within urban areas. While we have limited data on nest predator assemblages at our sites (Buxton and Benson ), nest predation was indeed lower in more urban areas. If birds also select habitat on the basis of conspecific or avian heterospecific presence, then lack of these cues in urban sites could also result in habitat avoidance (Valone ).…”

“…From mid‐May to early July in 2012 and 2013, we conducted bird surveys on 30 sites located on an urban‐to‐rural gradient throughout Cook, DuPage, Kane, and McHenry Counties, Illinois, and examined nest success at a subset of sites ( n = 9) as part of a larger concurrent study examining the effects of urbanization on grassland‐nesting birds (Fig. ; Buxton and Benson , ). Sites were dominated by grassland vegetation and included native warm‐season grasses and non‐native cool‐season grasses maintained by the county forest preserve districts.…”