Jul 16 2013
Though the solstice was more than three weeks ago the sun still hasn’t set in the Arctic. Some arctic animals have no circadian rhythm because there’s no light/dark cycle. What do the birds do?
The Max Planck Institute of Ornithology studied four species that nest near Barrow, Alaska. What they found is that some stayed on a 24-hour clock while others had no daily pattern. Their circadian rhythms varied based on lifestyle, sex and breeding stage. Here are the four they studied:
- Semi-palmated sandpipers are totally monogamous and share incubation and child rearing.
- Pectoral sandpiper males have multiple wives. Only the females incubate and take care of the kids.
- Red phalaropes reverse these roles. The females have multiple husbands. Only males incubate and raise the kids.
- Lapland longspurs are monogamous with the occasional male having multiple mates. Both parents take care of the kids but only the female incubates.
During the courtship period the shorebirds showed no daily pattern while the lapland longspurs simplified their lives by never giving up their 24-hour clock.
Incubation changed the shorebirds’ clocks. In summertime the ground temperature in Barrow varies daily from near freezing (11:00pm to 7:00am) to 60 degrees F (noon to 6:00pm). As soon as incubation began the incubating parents — pectoral sandpiper females and red phalarope males — began to follow a daily clock so they’d be on the nest when it’s cold.
The exception were the semi-palmated sandpipers. Because they completely share parental duties they threw out the clock when incubation began and synched as couples. “Who cares what time it is. We have each other.”
Meanwhile the pectoral sandpiper males and red phalarope females never stopped courting so they never developed a daily rhythm.
In the end the study shows that arctic-nesting birds are very flexible. They can be active regardless of time of day, then alter their circadian clocks when their needs change.
Those needs will change soon. The sun will set for the first time on August 1 and the birds will prepare to leave. For some shorebirds, migration has already begun.
(photo of a female red phalarope in Barrow, Alaska from Wikimedia Commons. Click on the image to see the original)