Estimation of flight-feather moulting periods of Rhinoceros Auklets Cerorhinca monocerata and Tufted Puffins Fratercula cirrhata using web images

Abstract

Moulting occurs in birds to maintain flying ability and thermoregulatory function. While seabirds are known to moult primary feathers during either breeding or non-breeding season, it is difficult to determine moulting timings for species which moult during non-breeding season when they are at sea. Most of previous studies used carcasses and specimen to determine timings of moult, which do not necessarily provide us the timings depending on a situation at collection. As a result, our knowledge of moulting timings particularly in seabirds are limited, and more practical methods are required for identifying moulting timings. The Rhinoceros Auklet Cerorhinca monocerata and Tufted Puffin Fratercula cirrhata are medium-sized alcids, and their timings of moult are poorly understood. We estimated the moulting periods of Rhinoceros Auklets and Tufted Puffins by using available web images which we obtained through internet searches. We then further conducted field observations in a breeding colony of Rhinoceros Auklets on Teuri Island, Japan to investigate if the moulting events occur during breeding. We found that Rhinoceros Auklets moult from July to September, whereas Tufted Puffins do from August to September or later. Furthermore, our field observation confirmed that none of Rhinoceros Auklets moulted during breeding at least for a population on Teuri Island. This study shows the efficacy of web images to identify moulting timings of seabirds that are particularly difficult to observe at sea, and using web images can potentially expand our knowledges on seabird studies.