Demographic and ethological characteristics of crevice-nesting auks (Alcidae, Charadriiformes) in the colony on Talan Island, Sea of Okhotsk: changes over 20 yearsстатья
Статья опубликована в журнале из списка Web of Science и/или Scopus
Аннотация:Studies on seabird biology are usually conducted using local nesting colonies over relatively short periods of time. However, changes in environmental conditions or the current demographic state of a particular population can have a significant impact on the behavior of individuals of certain species, becoming noticeable in long-term research. In the present study, we evaluated the return rate of adults to their breeding sites, the frequency of mate and nest chamber change, and the occurrence of club pairs in four auk species, namely, the crested auklet (Aethia cristatella), the parakeet auklet (A. psittacula), the horned puffin (Fratercula corniculata), and the tufted puffin (F. cirrhata), all of which nested on Talan Island in the Sea of Okhotsk in the years 2008–2015. We compared our results with those obtained for the same colony in 1989–1991 using similar study methods. The breeding success in 1989–1991 was high in all species, while in the years 2008–2015 it was extremely low in both crested and parakeet auklets. Moreover, between these periods, the number of crested and parakeet auklets on the island decreased several times. In tufted puffins it dropped less significantly, whereas the number of horned puffins increased slightly. In the period 2008–2015, 339 crested auklets, 57 parakeet auklets, 38 horned puffins, and 44 tufted puffins were banded individually with colored rings. The average return rate to the colony for the next year during this period amounted to 77, 82, 66, and 85% for these species, respectively. As much as 62% pairs of the crested auklet and 46% pairs of the parakeet auklet broke up the next season, but only half of those pairs of both species broke up probably because of the death of one of the mates. In other cases, both mates reappeared in the colony and formed new pairs. The nest chamber was changed the next year in 16% crested auklets, 12% parakeet auklets, and 22% tufted puffins. From 13 to 18% of crested auklets, parakeet auklets, and horned puffins formed club pairs in addition to the main (breeding) pairs. We also recorded club pairs in the tufted puffin, as well as those in the parakeet auklet and the horned puffin, describing them for the first time. Our study showed that, despite the decline in the numbers of three species and the increased numbers of the fourth one that occurred over 20 years, the percentage of individual returns of all species to the colony the next year remained approximately the same. However, with a low and progressively declining number and a consistently low breeding success in crested and parakeet auklets, the frequency of their pair breakup increased slightly. On the other hand, the probability of nest chamber change for the crested auklet decreased. This may indicate decreased competition for nesting sites after the decline in numbers, as a result of which the majority of birds occupied the most optimal nest chambers.
