Reproductive manipulation in the whooping crane Grus americana

Published source details Kuyt E. (1996) Reproductive manipulation in the whooping crane Grus americana. Bird Conservation International, 6, 3-10.
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This study is summarised as evidence for the following.

	Action	Category
	Use captive breeding to increase or maintain populations of cranes Action Link
	Foster eggs or chicks of cranes with wild conspecifics Action Link
	Foster eggs or chicks of cranes with wild non-conspecifics (cross-fostering) Action Link
	Release captive-bred individuals into the wild to restore or augment wild populations of cranes Action Link

Use captive breeding to increase or maintain populations of cranes

A study between 1967 and 1991 (Kuyt 1996) found that the removal of 355 whooping crane, Grus Americana, eggs from a wild population in Northwest Territories and Alberta, Canada, to start a captive population, did not negatively affect the wild population, which increased from 48 to 146 birds during the study period, with no nests being abandoned. The captive population had high hatching success (78–100% for 50 eggs shipped to Patuxent Wildlife Research Centre in 1967-74, and 77% for 166 eggs shipped to Grays Lake National Wildlife Refuge in 1975-88) but ‘downy young’ suffered 68% mortality, mainly due to disease and anatomical abnormalities. However, cranes first bred in captivity in 1975 (in Patuxent), with five females laying 19 eggs in 1989 (nine hatching). This study is also discussed in ‘Release captive-bred individuals’, ‘Foster eggs or chicks with wild conspecifics’ and ‘Foster eggs or chicks with wild non-conspecifics (cross-fostering)’.
Foster eggs or chicks of cranes with wild conspecifics

A small study between 1986 and 1991 (Kuyt 1996) found that at least three ‘novice’ breeding pairs of whooping cranes Grus americana in a population in Northwest Territories and Alberta, Canada, successfully raised chicks when their own eggs were substituted for other eggs which were definitely fertile. Novice pairs normally have lower reproductive success than more experienced pairs. At least one pair with low breeding success was also provided with a fertile egg several days from hatching and successfully raised the chick. This study is also discussed in ‘Use captive breeding to increase or maintain populations’, ‘Release captive-bred individuals’ and ‘Foster eggs or chicks with wild non-conspecifics (cross-fostering)’.
Foster eggs or chicks of cranes with wild non-conspecifics (cross-fostering)

A study in Idaho, USA, between 1975 and 1991 (Kuyt 1996) found that 215 wild-sourced and 73 captive-bred whooping crane Grus americana eggs that were cross-fostered into sandhill crane G. canadensis nests had high hatching success (210 eggs hatching, 73% of total) but low fledging success (85 birds fledging, 30%), low survival (13 individuals alive in 1991, 5%) and no pairs formed between fostered individuals. Causes of mortality included predation by coyote Canis latrans and birds, collisions with fences and powerlines and disease. This study is also discussed in ‘Use captive breeding to increase or maintain populations’, ‘Foster eggs or chicks with wild conspecifics’ and ‘Release captive-bred individuals’.
Release captive-bred individuals into the wild to restore or augment wild populations of cranes

A replicated study in Idaho, USA, between 1975 and 1991 (Kuyt 1996) found that 215 wild-sourced whooping crane Grus americana eggs that were cross-fostered into sandhill crane G. canadensis nests had higher hatching success than 73 captive-bred whooping crane eggs, fostered at the same time (77% hatching success for wild-sourced eggs vs. 60% for captive-bred). This study is also discussed in ‘Use captive breeding to increase or maintain populations’, ‘Foster eggs or chicks with wild conspecifics’ and ‘Foster eggs or chicks with wild non-conspecifics (cross-fostering)’.