WCEP Statement on Nesting Studies

October 2009

This spring, 12 breeding pairs of whooping cranes built nests and laid eggs. All 12 nests failed earlier this spring and five pairs renested. Of those five pairs, two pairs each hatched a chick. Unfortunately, neither of the chicks survived to fledging.

The nest abandonment pattern this spring is similar to what has been observed in previous years. The Whooping Crane Eastern Partnership (WCEP) investigated the cause of the abandonments through analysis of data collected throughout the nesting period on crane behavior, temperature, food availability, and black fly abundance and distribution.

2009 nesting studies did not provide data that indicated whether black flies were causing the cranes to abandon incubation before eggs hatched. However, observers did note in some cases that the abundance of black flies near crane nests appears to be much higher than would be expected from levels monitored elsewhere in the refuge during the same time period.

The results of these studies are still being analyzed, but are unlikely to result in conclusive evidence of causes of nest failure after only one study season. Scientific experiments have greater power to reveal the causes of observed results when the size of the sample is large. Due to the small number of nesting pairs, it is difficult to draw valid conclusions about cause and effect relationships affecting nesting success of the whooping cranes. In addition, incubating cranes are exposed to a large number of stresses, and it is likely that several factors may be affecting the cranes, quite possibly in combination.

WCEP plans to continue intensive nest monitoring in 2010, and additional techniques are being explored to monitor crane behavior and conduct a management experiment that seeks to remove black flies from the nest areas to determine correlation between black flies and nesting failure.

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Last updated: October 4, 2009