Incubation and nesting behaviour of the Chestnut-collared Longspur

Abstract

Incubation strategies by birds are central to reproductive success, particularly for species in which only one parent incubates the eggs. Incubating adults must behave in ways that allow them to maintain their own nutritional requirements while meeting the needs of the developing embryos. Ambient temperature, time of day, time of season and embryo development are known to influence incubation activities. We used video records to assess the effects of these factors on Chestnut-collared Longspur (Calcariusornatus; hereafter longspurs) incubation attentiveness. Very little research has documented aspects of longspur incubation patterns and knowledge of their nesting behaviour is limited. We analyzed 770 h of daytime video footage from 13 nests monitored in southwestern Saskatchewan, Canada in 2010. Incubation attentiveness was strongly influenced by time of day and was highest during the morning (0500–600 hours Central Standard Time (CST), midday (1100–1500 hours CST) and evening (2000–2100 hours CST) periods. Females increased nest attentiveness and made fewer departures during these times. Such a schedule is likely related in part to egg temperature and warming or cooling rates of the clutch. Overall, female longspurs incubated 62 % of the time during daylight hours and were on the clutch constantly through the night. Video surveillance also allowed us to document males sitting on eggs and provisioning incubating females, and nest predation by Richardson’s Ground Squirrels (Urocitellus richardsonii). Our research identifies time of day as an important factor influencing longspur incubation behaviour, but further research is required to determine the role of nest and egg temperatures. We recommend longspur researchers conduct nest searching in the early morning and late evening to increase the likelihood of flushing incubating females.