PARENT SESSION
Contributed Oral Session 52: Avian Nesting and Breeding
Tuesday, August 9, 8:00 AM - 11:30 AM, Meeting Room 524 A, Level 5, Palais des congrès de Montréal

Differentiate between habitat and social drivers of nest aggregations using point pattern analysis.

Melles, Stephanie^*,1, Fortin, Marie-Josée¹, Csillag, Ferko¹, Badzinski, Debbie², ¹ University of Toronto, Toronto, ON, Canada² Bird Studies Canada, Port Rowan, ON

ABSTRACT- Many species of birds tend to have an aggregated nesting pattern. Even highly territorial species like the Hooded Warbler (Wilsonia citrina) seem to be semi-colonial at certain scales. The implication of spatial clustering in birds is that the actions of individuals are not independent. A number of competing factors and/or behaviours may drive this type of pattern. We used Ripley's L-function to analyze the point pattern of data on nest locations collected over a 6 year period (1999 - 2004) in a 1213 ha forest. Two dominant hypotheses were evaluated using Monte Carlo simulation techniques. We tested whether nests were aggregated merely because the preferred nesting habitat was also aggregated (Null_{1, HABITAT}), and found that nest sites were randomly distributed within suitable nesting habitat at almost all scales, except intermediate ones. We tested whether this additional aggregation was related to the locations of unmated males and/or other mated males in the area (Null_{2, SOCIAL}). Nests were significantly associated with unmated males only at two scales, 420m and 780m. However, females preferred to nest more closely to other mated males at even smaller scales (120 and 180 m, and between 240 and 400 m). This indicates that females pack their nests more tightly than the available habitat requires in order to be situated as closely as possible to their neighbours mates. Point pattern analysis is an underutilized technique that can be used to help recognize behaviours most relevant to the creation of pattern at multiple scales, from local population dynamics to landscape level effects.

Key words: Ripley's K, Null models, Clustered breeding