Effects of Elevation on Trap Behavior in Mountain White-crowned Sparrows (<i>Zonotrichia leucophrys oriantha</i>)

Abstract

The Mountain White-crowned Sparrow(Zonotrichia leucophrys oriantha) is a migratory songbird that nests in alpine and sub-alpine meadows in the Rocky Mountains. They return to their natal elevation to breed, and nest from 2,438m to 3,657m above sea level in the spring to late summer. Because they nest at such high elevations, these birds have adapted to endure increased solar heating, low nocturnal temperatures, sudden intense storms, large interannual variations in residual snowpack, a shorter growing season, lower plant productivity, and seasonal delays in insect and fruit emergence (Körner 2003). As the elevation increases each of these effects of elevation increase or intensifies as well; hence, habitat at low elevation would be considered higher quality and we would predict to see more competitive and aggressive individuals establish territories in these areas. The ideal despotic distribution theory states that competitive individuals occupy the preferred elevations and habitats, while inferior competitors breed in suboptimal habitats that are typically higher in elevation (Bear et al. 2009). With such differences in elevation I hypothesized that at lower elevations we will see more active and more aggressive birds due to the abundance in high quality habitat and a high number of competitors. Data was collected from June 1st 2016 to August 1st 2016. Behavioral response data was collected by recording the activity of each bird in the trap for 15 seconds. The duration of each activity performed within the 15 seconds was recorded. To analyze the data we broke the activities down into three categories—low activity, high activity and damaging activity—and assigned each individual action to a category. Our results came out to be significant between high elevation low activity and low elevation low activity (P=0.00033) and showed that birds at low elevation displayed significantly more low activity responses than birds at high elevation. My results did not support my hypothesis nor does it support the ideal despotic distribution theory. With this as the pilot study I believe more research should be done to gather a larger sample size to better understand why these results did not support this well tested theory.

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