George’s latest field report describes his daily nest checks as parents are feeding chicks to prepare them for fledging.
This year, with ice visible north of the island until a few days ago, there was an abundance of Arctic Cod. A walk through the colony found many parents flying back to their nests with adult cod (some bigger than six inches). Chick weights and survival reflected this abundance with no mortality of nestlings yet being recorded this year.
However, since sea ice was blown offshore by strong south winds two days ago, most chicks have been losing weight with others having little or no growth. Based on what we have seen in past years, parent birds should soon be shifting their prey choice to the more predictable – but less preferred – sculpin. The abundance of sculpin – which are present in a range of water temperatures – and the parents’ ability to shift their foraging strategies will determine the fledging success of the nestlings this year.
Read about this year’s nest checks and growth rates at Proteus.
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Graduate student Drew Sauve recently returned from Cooper Island. He describes his collaboration with George in this guest post.
The Black Guillemots on Cooper Island are one of many wild populations that are responding to climate change by changing when they lay their eggs. These Arctic seabirds want to lay their eggs as soon as the winter snow melts and spring begins, because their breeding season—from first access to a nest cavity to departure of chicks—is 80 days, an exceptionally long breeding period for a bird. Parent guillemots have to have their young ready to fly off to sea before fall snow accumulation begins to block entrances to nest cavities. In recent years, with sea ice retreating offshore in late summer, early breeding has the benefit of being able to provision young when the preferred prey of Arctic Cod is still readily available.
While there are decades of data that show spring snowmelt is occurring earlier in northern Alaska and, allowing guillemots to lay their eggs earlier, my research is focused on whether Black Guillemots are evolving to lay their eggs earlier.
Read the full post at Proteus.
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August 11, 2018: Field report
Hatching is finally over with one very late egg hatching today after having been incubated for 34 days; 28 days is normal. The oldest nestling is 16 days old; the chick is gaining weight and doing well like all of the other 45 nestlings.
While the main pack ice is well offshore, the Marginal Ice Zone, where ice covers from 18 to 80 percent of the ocean’s surface, extends south to the entire Alaskan Beaufort Sea coast, including Cooper Island. The seascape visible from the north beach now has widely scattered floes, some with rather high vertical relief breaking the horizon, in a nearly flat calm sea. This differs greatly from what was present last year when the first week in August had no ice visible with large swells breaking on north beach. More importantly, last year at this time the sea surface temperature was well above 4 degrees Celsius while this year it is less than 2 degrees Celsius. The guillemot’s preferred prey, Arctic Cod, are typically found in waters from -2 to 4 degrees.
The ice and water temperature conditions are ideal for the parent birds provisioning. Arctic Cod has comprised well over 90 percent of the prey being fed to chicks this year. The two oldest chicks, hatched on July 21, weighed 35 grams at hatching and now weigh 275 grams and 245 grams – the larger of the two experiencing an almost seven-fold weight increase in a 15-day period. A growth rate that rapid requires readily available prey that is both abundant and high energy, as well as two dedicated parents to return to the nest site with a fish every hour. Similar high growth rates are occurring at other nests.
Read the rest of the field report at Proteus.
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