A reply to Dhondt: broodedness and latitude affect the response of reproductive timing of birds to food supplementation
- PDF / 123,674 Bytes
- 3 Pages / 595.276 x 790.866 pts Page_size
- 80 Downloads / 141 Views
COMMENT
A reply to Dhondt: broodedness and latitude affect the response of reproductive timing of birds to food supplementation Stephan J. Schoech
Received: 26 May 2010 / Accepted: 9 June 2010 / Published online: 29 June 2010 Dt. Ornithologen-Gesellschaft e.V. 2010
Schoech and Hahn (2007, 2008) used a meta-analysis to test the hypothesis that the responsiveness of female birds (in terms of advancement of clutch initiation) to supplemental food was negatively correlated with latitude. Their analysis found some support for this hypothesis, and the authors listed six additional factors that might help to explain the unexplained variance in their model. Dhondt (2010) proposes that broodedness (i.e., the laying of a second or third clutch and attempts to rear subsequent broods after successfully rearing an initial brood), a factor not considered or mentioned in the original work, may better explain the documented patterns. While we have always encouraged consideration of other explanations of the observed patterns, I find Dhondt’s synthesis to be problematic, primarily because of seemingly errant broodedness assignments for a number of species. Most would agree that it is necessary to consider the life history traits and environmental conditions that characterize the specific population under study. For example, the length of the breeding season (and invariably the number of broods will be determined in part by this variable) could be expected to vary by latitude, elevation, micro-habitat (i.e., temperature that may vary with distance from a modulating body of water), among others. In other words, it is essential that one knows how many broods are reared by the females of the specific population that has been incorporated into the Schoech and Hahn analysis. I first noted that the Florida Scrub-Jays (Aphelocoma coerulescens), a species that I
Communicated by F. Bairlein. S. J. Schoech (&) Department of Biological Sciences, University of Memphis, Memphis, TN 38152, USA e-mail: [email protected]
have used as a research model for some 20 years, was misassigned. While Dhondt states that he used ‘‘the relevant species account in The Birds of North America (Poole 2005)’’ to extract broodedness assignments, the contribution of Woolfenden and Fitzpatrick on the Florida ScrubJay to The Birds of North America (1996) states ‘‘True second brood attempts… are rare (36/916 pair year) in natural settings such as Archbold Biological Station with most years having none.’’ Where Dhondt may have been confused is the subsequent sentence that notes ‘‘Second broods more frequent (up to 30% of pairs attempt) where supplemental food provided (Bowman et al. 1995).’’ The research by Bowman et al. was conducted in a suburban development where multiple factors make this a very different environment from that of the ‘wildlands’ of the Archbold Biological Station (ABS), factors which result in numerous differences in breeding phenology (Bowman and Woolfenden 2002; Fleischer et al. 2003; Schoech and Bowman 2003; Shawkey et al. 2004). The two s
Data Loading...
