Honors Students' Abstracts
Changes in Reproductive Timing: An Analysis of California House Finches
Tauras Vilgalys
House finches breed over a wide geographic range covering much of the United States and Mexico. Historically, this nesting has shown broad synchrony with house finches breeding from March to July. In a number of other bird species, there have been trends to breed earlier in response to changing environmental conditions over recent decades. This study undertakes a detailed examination of the breeding season of Californian house finches examining the trends in reproductive timing over time. Data were taken from historical nest records maintained at the Western Foundation of Vertebrate Zoology from 1882 to 2007. Examining the earliest and latest reported nests across decades, there is no trend in the onset of breeding. However, the breeding season has been terminating earlier in recent years. One possible explanation for this decreasing trend is the temperature inhibition of reproduction. From an analysis of historical temperature data, there appears to be a relationship between increasing temperature and the earlier termination of reproduction. Future research will directly test for an effect of temperature on reproductive termination using live birds and a more thorough comparison of nest records to historical temperature data.