An inexpensive method for quantifying incubation patterns of open-cup nesting birds, with data for Black-throated Blue Warblers

Quantifying incubation patterns has often involved long observation periods in the field, video cameras, or the use of other electronic devices that s ometimes require the partial destruction of clutches and insertion of artif icial eggs. In this study: we used an inexpensive, nondestructive method in volving temperature probes combined with data loggers to examine the incuba tion rhythm of female Black-throated Blue Warblers (Dendroica caerulescens) . The method provided detailed records of on-off patterns fur females for s elected 24-h periods during incubation. Female warblers spent an average (/- SE) of 64.0% of daylight hours incubating in bouts lasting 20.5 +/- 1.5 min and made 2.4 +/- 0.1 departures from the nest/h on trips that lasted 10 .6 +/- 0.7 mill. incubation bouts were longer and females spent more time i ncubating per hour in the mornings and late afternoons than at mid-day. Old er females had longer incubation bouts and tended to have shorter incubatio n periods than did yearling females, suggesting that experienced individual s were more effective incubators. Because of its ease of use and because ne sts with probes were not depredated at a higher rate than controls. we sugg est that the temperature probe/data logger method is an efficient and effec tive way to quantify incubation rhythms for open-cup nesting birds.