Title
Behavior of Prairie Falcons (Falco mexicanus) During the Nesting and Fledging-Dependence Periods Under Fluctuating Prey Conditions
Document Type
NCA Publications/Journals & Book Chapters
Publication Date
6-1-1996
Journal Title/Publication Source
Bird Behavior
Volume
11
Page Numbers
81-89
Abstract
We studied the behavior of adult and young prairie falcons (Falco mexicanus) during the nesting and fledging-dependence periods over a period of years when the population density of their primary prey, Townsend's ground squirrels (Spermophilus townsenii), dramatically declined. The percentage of time adult male falcons spent in their nesting territories during the early brood-rearing period was significantly higher in 1992, the year of greatest ground squirrel abundance, than in 1991, a moderately high prey year, or in 1993 and 1994, the low prey years. Mean prey delivery rates during the entire brood-rearing period were similar among all years, but rates increased as nestlings aged in 1992, whereas they decreased as nestlings agged in 1991, 1993, and 1994. Prent falcons delivered proportionally fewere ground squirrels and small mammals, but more birds and reptiles in 1993 and 1994 than in 1992. This increased use of alternative prey likely represents compensation for low ground squirrel abundance. The ages at which falcons dispersed from their natal territories were similar between 1992 and 1993. However, low ground squirrel abundance may explain why the length of the staging period (the time between dispersal from the natal territory and emigration from the study area) was significantly lower in 1992 than in 1993.
Publication Information
McFadzen, Mary E. and Marzluff, John M., "Behavior of Prairie Falcons (Falco mexicanus) During the Nesting and Fledging-Dependence Periods Under Fluctuating Prey Conditions" (1996).
Bird Behavior
, 11, 81-89
https://scholarworks.boisestate.edu/bop/Bibliography/Bibliography/292
Behavior of Prairie Falcons (Falco mexicanus) During the Nesting and Fledging-Dependence Periods Under Fluctuating Prey Conditions
We studied the behavior of adult and young prairie falcons (Falco mexicanus) during the nesting and fledging-dependence periods over a period of years when the population density of their primary prey, Townsend's ground squirrels (Spermophilus townsenii), dramatically declined. The percentage of time adult male falcons spent in their nesting territories during the early brood-rearing period was significantly higher in 1992, the year of greatest ground squirrel abundance, than in 1991, a moderately high prey year, or in 1993 and 1994, the low prey years. Mean prey delivery rates during the entire brood-rearing period were similar among all years, but rates increased as nestlings aged in 1992, whereas they decreased as nestlings agged in 1991, 1993, and 1994. Prent falcons delivered proportionally fewere ground squirrels and small mammals, but more birds and reptiles in 1993 and 1994 than in 1992. This increased use of alternative prey likely represents compensation for low ground squirrel abundance. The ages at which falcons dispersed from their natal territories were similar between 1992 and 1993. However, low ground squirrel abundance may explain why the length of the staging period (the time between dispersal from the natal territory and emigration from the study area) was significantly lower in 1992 than in 1993.