Open AccessAssessing the influence of geography, land cover and host species on the local abundance of a generalist brood parasite, the brown‐headed cowbird
Author(s) -
Cummings Katherine,
Veech Joseph A.
Publication year - 2014
Publication title -
diversity and distributions
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.918
H-Index - 118
eISSN - 1472-4642
pISSN - 1366-9516
DOI - 10.1111/ddi.12139
Subject(s) - cowbird , species richness , brood parasite , generalist and specialist species , abundance (ecology) , ecology , context (archaeology) , passerine , geography , host (biology) , habitat , biology , breeding bird survey , macroecology , parasitism , archaeology
Aim The brown‐headed cowbird is an obligate brood parasite known to exploit a large number of host species and use a variety of habitats. Much attention has been directed towards uncovering the fundamental factors that affect cowbird abundance; however, no study has evaluated these factors in the context of a biogeographic‐scale analysis that takes into account spatial autocorrelation. Our primary objective was to compare the relative influence of geography, land cover and host species on the local abundance of cowbirds. Location Great Plains region of the USA . Methods We used data from the N orth A merican B reeding B ird S urvey and the N ational L and C over D atabase to examine the relationships between cowbird abundance and host species, land cover composition and geographic location of a survey route. Multiple regression models were developed for various combinations of these factors. To control for spatial autocorrelation, we used SAM 4.0 ( S patial A nalysis in M acroecology) software to implement simultaneous autoregressive modelling of the error term. We then used a model comparison approach to identify the factors that most influence cowbird abundance. Results Among all models examined, host species richness was the single most strong predictor and the sole statistically significant predictor. Cowbird abundance increased with host species richness but did not change in any significant way with non‐host passerine richness or abundance of host species. Models with land cover variables tended to have the poorest fit to the cowbird abundance data. Main conclusions Our results suggest that cowbirds may be attracted to areas with greater host richness and/or recruit better in such areas, although our data did not allow direct examination of either process. In a greater context, our study demonstrates the utility of a spatially based and geographically extensive analysis in finding range‐wide factors that affect the local abundance of a species.