Nest predation and habitat selection in the grasshopper sparrow (Ammodramus savannarum)

nest predation;Grasshopper Sparrow;grassland birds;fire and grazing;habitat selection

Lyons, Timothy ; Miller ; James R.

关键词: nest predation;    Grasshopper Sparrow;    grassland birds;    fire and grazing;    habitat selection;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/45458/Timothy_Lyons.pdf?sequence=1&isAllowed=y

美国|英语

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

【 摘 要 】

Predation is the leading cause of nest failure for many birds and is an important source of natural selection that shapes avian behavior and life-history traits. However, our understanding of the relationship between habitat characteristics and nest loss and how predation affects nest-site selection is limited. Predators are not often identified, yet their behavior greatly influences nest loss patterns. Most studies of nest-site selection make unrealistic assumptions about the ability of birds to identify and access preferred habitat and few use unambiguous measures of selection. I studied how grassland management with fire and grazing influences predator-specific patterns of nest loss and whether predation influenced nest-site selection by grasshopper sparrows (Ammodramus savannarum). I used near-infrared video cameras to identify nest predators and followed breeding females on multiple nesting attempts within a breeding season. Burning reduced losses by snakes (Thamnophis and Coluber spp.), whereas predation by mammals and snakes increased with litter cover and fescue (Schedonorus phoenix) surrounding the nest. Mammals were less likely to prey upon nests with increased forb cover as well. Nest losses attributed to cowbirds (Molothrus ater) were unrelated to measured habitat or landscape variables and unaffected by management actions. Though nest sites did not differ from available habitat, female grasshopper sparrows did exhibit adaptive nest-site selection by selecting safer locations on subsequent breeding attempts. My results support that the use of fire can reduce nest loss, but success is contingent on predator identity. Reductions in litter and fescue and increasing forb cover can reduce predation as well. Further, grasshopper sparrows’ nest-site selection is adaptive in terms of reducing nest loss, but females make more adaptive choices when re-nesting. This information can help devise effective management strategies aimed at reducing nest loss and improve our understanding of avian behavior.