Nocturnal Provisioning by Swainson's Thrush

Publication Type:Journal Article
Year of Publication:2011
Authors:Ball, JR, Lukianchuk, KC, Bayne, EM
Journal:The Wilson Journal of Ornithology
Volume:123
Issue:3
Date Published:2011
ISBN Number:1559-4491
Keywords:Catharus, Catharus ustulatus, Hylocichla, Hylocichla ustulata, Turdidae
Abstract:Abstract We studied Swainson's Thrush (Catharus ustulatus) at two study areas of different latitudes to examine if parents provisioned their nestlings beyond daylight hours. We viewed 591 hrs of video from 37 nests. All nests were provisioned outside the dawn to dusk period but provisioning also continued through the night at the northern site. Night provisioners made an average (± SE) of 1.55 ± 0.18 fewer provisioning trips/hr during the pre-dawn to late evening periods compared to non-night provisioners. Night provisioners compensated with two additional trips/hr during the post-dusk period and 2.11 (95% CI: 1.61?2.77) trips/hr during the night period. Night provisioners did not experience improved reproductive success, which supports our conclusion that night provisioning was compensatory rather than ?bonus? energy. Nocturnal provisioning was best explained by increased day length, which corresponded to increased light levels during the night period that enabled parents to navigate and locate food. Swainson's Thrush extend a given provisioning effort over more hours as light levels permit rather than increasing energy delivery to their nestlings, which may provide time and energy for other activities.Abstract We studied Swainson's Thrush (Catharus ustulatus) at two study areas of different latitudes to examine if parents provisioned their nestlings beyond daylight hours. We viewed 591 hrs of video from 37 nests. All nests were provisioned outside the dawn to dusk period but provisioning also continued through the night at the northern site. Night provisioners made an average (± SE) of 1.55 ± 0.18 fewer provisioning trips/hr during the pre-dawn to late evening periods compared to non-night provisioners. Night provisioners compensated with two additional trips/hr during the post-dusk period and 2.11 (95% CI: 1.61?2.77) trips/hr during the night period. Night provisioners did not experience improved reproductive success, which supports our conclusion that night provisioning was compensatory rather than ?bonus? energy. Nocturnal provisioning was best explained by increased day length, which corresponded to increased light levels during the night period that enabled parents to navigate and locate food. Swainson's Thrush extend a given provisioning effort over more hours as light levels permit rather than increasing energy delivery to their nestlings, which may provide time and energy for other activities.
URL:http://dx.doi.org/10.1676/10-137.1
Short Title:The Wilson Journal of Ornithology
Taxonomic name: 
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith