Individual study: Effects of food supplementation on the timing of nest initiation in belted kingfishers
Kelly J.F. & Van Horne B. (1997) Effects of food supplementation on the timing of nest initiation in belted kingfishers. Ecology, 78, 2504-2511
Food availability is an important factor affecting the time of nesting in birds, but few data are available for pisciverous birds.
Belted kingfisher Ceryle alcyon nests were located and monitored along 20 km of the Cache le Poudre River during the breeding seasons from 1992 to 1995. The river banks were examined weekly from March-June for burrows and adult kingfishers. During 1992 most nests were identified during the incubation period. From 1993-1995 most were identified at the burrowing stage. Identified nests were watched for 1-2 hrs every fourth day, and all behaviour of adult bids was recorded. To avoid disturbance, the nest burrows were not excavated during egg-laying or incubation. The perching of female kingfishers outside the burrow for long periods was found to be coincident with egg-laying. Adults became noisy after hatching and brought more food to the burrow. The midpoint between the dates of these two behaviour changes was taken as an estimate of the laying date of the first egg. When nestlings were 7-10 days old, the nest chamber was accessed from the top of the bank, and the nestlings were weighed, measured and individually marked. Nestlings were reweighed and measured every fourth day.
In 1993, 1994 and 1995 eight feeding stations were established at 2 km intervals along the river. The spacing was selected to ensure that fed and control pairs were interspersed. Kingfishers are very territorial, and it was unlikely that control pairs would steal significant quantities from fed pairs.
In 1992-1995, nests of 14, 10, 17 and 15 pairs of kingfishers were identified, of which 5, 7 and 8 pairs used supplemented food in 1993, 1994 and 1995 respectively. In 1994 one pair and in 1995 two pairs of birds foraged at a fish hatchery. These pairs were excluded from analysis.
- During 1993, supplementation with 20-30 g of fish was started on 20 April. There was no difference in initiation dates between supplemented and control nests.
- In 1994 and 1995, supplementation with 90-100 g of fish was started on 8 March
Nest initiation dates were significantly earlier with supplemented than control nests for the relevant year. There was no interaction between year and food effect.
The mass of kingfisher broods relative to published data declined significantly from early to late in the breeding season. Kingfishers that nested early had heavier nestlings and were more likely to have a second brood in the event of nest failure than later-nesting birds.
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