AVIS-IBIS

Birds of Indian Subcontinent

Breeding Patterns of Henslow's Sparrow and Sympatric Grassland Sparrow Species

Publication Type:Journal Article
Year of Publication:2010
Authors:L. Dornak, L
Journal:The Wilson Journal of Ornithology
Volume:122
Issue:4
Date Published:2010
ISBN Number:1559-4491
Keywords:Ammodramus, Ammodramus henslowii, Ammodramus humeralis, Ammodramus sandwichensis, Ammodramus savannarum, Ammospiza, Ammospiza henslowii, Emberizidae, Myospiza, Myospiza humeralis, Nemospiza, Nemospiza henslowii, Passerculus, Passerculus sandwichensis, Passerherbulus, Passerherbulus henslowii
Abstract:Abstract Henslow's Sparrows (Ammodramus henslowii) are reported to have irregular patterns of return to breeding areas. I present data supporting these reports at rangewide extents, while testing potential biases inherent in the North American Breeding Bird Survey data. Two measures of population variability were used to show that Henslow's Sparrows are less likely to use breeding areas predictably and consistently, but have similar variance in numbers at occupied sites relative to other sympatric grassland sparrow species. I illustrate how restricting analyses to single-observer-collected Breeding Bird Survey data results in subtle but significant effects not detected in data aggregated from multiple observers through the study period. The most conservative analysis (single-observer, restricted distribution) showed that Henslow's Sparrows exhibited lower prevalence of occurrence than Grasshopper (Ammodramus savannarum) (P < 0.001) and Savannah (Passerculus sandwichensis) (P < 0.001) sparrows but no difference in variation of abundance (P > 0.05). These results suggest Henslow's Sparrows are not returning to previously used breeding habitat from year-to-year. Grassland management should consider the behavior documented in this study and attempt to incorporate this facet of Henslow's Sparrow biology into decisions that involve broad-scale landscape design.Abstract Henslow's Sparrows (Ammodramus henslowii) are reported to have irregular patterns of return to breeding areas. I present data supporting these reports at rangewide extents, while testing potential biases inherent in the North American Breeding Bird Survey data. Two measures of population variability were used to show that Henslow's Sparrows are less likely to use breeding areas predictably and consistently, but have similar variance in numbers at occupied sites relative to other sympatric grassland sparrow species. I illustrate how restricting analyses to single-observer-collected Breeding Bird Survey data results in subtle but significant effects not detected in data aggregated from multiple observers through the study period. The most conservative analysis (single-observer, restricted distribution) showed that Henslow's Sparrows exhibited lower prevalence of occurrence than Grasshopper (Ammodramus savannarum) (P < 0.001) and Savannah (Passerculus sandwichensis) (P < 0.001) sparrows but no difference in variation of abundance (P > 0.05). These results suggest Henslow's Sparrows are not returning to previously used breeding habitat from year-to-year. Grassland management should consider the behavior documented in this study and attempt to incorporate this facet of Henslow's Sparrow biology into decisions that involve broad-scale landscape design.
URL:http://dx.doi.org/10.1676/10-016.1
Short Title:The Wilson Journal of Ornithology
Taxonomic name: 
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith