Peak abundance of active nests can be reliably determined from a single count conducted during peak nesting season because of the conspicuous nature of active BCNH nests (Kelly et al.
The ratio of young to active nests, or young to nesting pairs, is frequently used to quantify reproductive success in colonial birds including BCNH (e.
Young were unlikely to have dispersed before the peak abundance censuses on 14 June 2010 and 8 June 2011 because BCNH disperse at approximately 58 d of age (Levengood et al.
Because of the endangered status of BCNH in Illinois and under advisement of the Illinois Department of Natural Resources observation methods involving touching BCNH (e.
The close proximity of two habitat patches (grove and avenue) and my ability to census the entire BCNH colony daily presented an opportunity to investigate whether the colony exhibited behavioral flexibility in terms of fine-scale habitat patch selection in response to fluctuations in colony size.
To determine the effect of colony size on habitat patch selection, I used logistic regression wherein the habitat patch selection of an individual BCNH was the binary dependent variable of interest.
total]), defined as the number of adult BCNH in the colony determined via census.
BCNH nested in very high density in Lincoln Park, with 217 nests/ha in 2010 and 315 nests/ha in 2011.
In 2010 although many BCNH pairs initially began nesting on the grove, only one pair remained there for the entire breeding season and they did not produce young.
colony] was number of BCNH in the colony and y was a categorical variable for year (2010 or 2011).
In both 2010 and 2011, it was more probable that a BCNH would not select the avenue (and would therefore select the grove) at low colony sizes and would select the avenue at high colony sizes (Fig.
BCNH in North America in natural habitats typically nest in high densities such as 62 nests/ha (Bent, 1963) and 88 nests/ha (Hoffman and Prince, 1975).