Behavioral Observation and Paternal Investment of Eastern Kingbirds at Malheur National Wildlife Refuge

Abstract

Chapter 2 was split into three distinct questions: 1) are parental nesting behaviors repeatable, 2) is a one hour sample sufficient to capture variability in these behaviors, and 3) is the first hour of recording sufficient to capture variability in these behaviors. I found overwhelming evidence that the behaviors I measured were repeatable. This is important because lack of repeatability would call into question the use of single point samples of behavior to study animal behavior. I similarly found strong evidence that a one hour sample was sufficient to capture variability in parental behaviors. From this I was able to suggest that further sampling effort would be better ii spent increasing sample size rather than observation length. Results of my test of whether the first hour of recording captured accurately variability in parental behavior was less clear. While a positive correlation usually existed between behaviors recorded in the first hour and recordings made over a 2 to 3 hour observation period, most behaviors also tended to have significantly lower values in the first hour. I tested whether this was the result of a lingering observer effect or a natural effect of time of day and concluded that an observer effect was the more likely explanation.In recent decades behavioral ecologists have shown that a majority of songbirds that breed as socially monogamous pairs are rarely genetically monogamous. This creates a conundrum for males, and in chapter 3 I address a question of long-standing debate among behavioral ecologists studying the extra-pair mating systems of birds; does loss of paternity lead to reductions in a male's investment in his social mate's current brood. I used the standard male feeding rate as a measure of male investment as well as a far more nuanced measure derived from the first eigenvector of a principal component analysis of six paternal behaviors. These were both tested using Akaike's Information Criterion against a number of variables likely to affect parental behavior, including realized paternity. Ultimately, I found no evidence that kingbirds were able to affect paternal investment in response to lost paternity, and conclude that they likely had no means to assess realized paternity within the nest of their social mate. However, from the other parameters tested I found that males increased their investment as brood size increased and as the female spent more time attending, but not feeding, the iii nestlings. Also, male investment decreased as territory density increased and flight feather length increased. Theory surrounding the variability of extra-pair paternity in birds can be used to account for these results. In a denser population males are predicted to reduce paternal effort for one of two reasons; increased likelihood of paternity loss in his own nest and an increased investment in pursuing extra-pair copulations of his own. Longer flight feathers are a sign of greater age and quality in kingbirds, so males with this trait are expected to spend more time pursui...