Author: Nicholas Ryan Peterson

Publisher:

Published: 2006

Total Pages: 118

ISBN-13:

Loggerhead Shrikes (Lanius ludovicianus) have been declining in the United States since the 1960s, and in Kentucky they declined by 9.6% from 1980-2003. Suggested causes for their decline include eggshell thinning due to DDT exposure, loss of suitable habitat, low reproductive success, and competition with exotic species in parts of their range. None of these, however, have provided a definitive reason for the decline. The objective of my study was to examine the reproductive success of Loggerhead Shrikes in central Kentucky and to determine the possible effect of habitat availability and suitability on the abundance and reproductive success of Loggerhead Shrikes. Shrikes were studied from 15 March-30 September 2005 in Madison and Garrard counties, Kentucky, and breeding adults were fitted with radio transmitters so that I could measure their territory sizes. Additionally, I measured nest-level and territory-level habitat characteristics and I also monitored active nests to assess reproductive success. Lastly, hunting behaviors and habitats were recorded. Mean territory (N = 12) size was 9.0 ha and nests (N = 18) were most often located in Eastern red cedar, Osage orange, and multiflora rose. Nest-level habitat characteristics of used and unused sites differed, with the percentage of bare ground and vegetation height within 10 m of nests being the best discriminating variables between such sites. there were no differences between the habitat characteristics of successful and unsuccessful nests, or between used and unused territories. Shrikes most often caught prey that were identified as arthopods and usually hunted from linear man-made structures such as fencelines and utility wires. Reproductive success was low in my study, with 50% of nests failing and only 42.8% of eggs resulting in fledglings. The availability of suitable breeding habitat does not appear to be a limiting factor in central Kentucky Loggerhead Shrikes populations, though low reproductive success prior to fledging may be a limiting factor. Low reproductive success of Loggerhead Shrikes in central Kentucky may be a result of recent increases in local avian and mammalian predators. Loggerhead Shrike management should focus on ensuring that nesting habitat is available in habitats that are not foraging corridors for mammalian predators (i.e., non-linear habitats), and Shrikes may also benefit from a hand-rearing program that increases the yearly production of young.