Heermann's Gull heermannii

(last update: 23-01-2018 )

Coordinators:
John Cant
Mars Muusse

Index ORG

ring projects
PDF's

1cy June
1cy July
1cy Aug
1cy Sept
1cy Oct
1cy Nov
1cy Dec

2cy Jan
2cy Feb
2cy March
2cy April
2cy May
2cy June
2cy July
2cy Aug
2cy Sept
2cy Oct
2cy Nov
2cy Dec

3cy Jan
3cy Feb
3cy March
3cy April
3cy May
3cy June
3cy July
3cy Aug
3cy Sept
3cy Oct
3cy Nov
3cy Dec

adult Jan
adult Feb
adult March
adult April
adult May
adult June
adult July
adult Aug
adult Sept
adult Oct
adult Nov
adult Dec

1st > 2nd cycle (2CY): July

By July these 2CY birds are in PB2 moult (complete moult in summer from April - August), Outer primaries still old juvenile in many birds, with central primaries being replaced. More advanced birds have the outer primaries shed, still growing, adding to a rather compact look due to short primary projection.

Steve N.G. Howell, Molt in North American Birds.

First-cycle molts in Laridae Gulls p149

Large gulls appear to have only a single molt added into their first cycle. Compared with the adult molts, this added molts resembles a prealternate molt in its extent and timing. But it also resembles a preformative molt when compared with the molts of small gulls with a complex alternate strategy. The puzzles of naming this molt, and how it may have evolved, are discussed in the family account for ibises and spoonbills.

The first-cycle molt of large gulls typically is partial and averages more extensive in southern-breeding species (such as California and Yellow-footed gulls) than in northern-breeding species (such as Thayer’s and Glaucous-winged gulls). Some individuals of high-latitude species, such as the Glaucous Gull, may even skip this molt altogether and in their first summer molt directly from juvenile (first basic) into second basic plumage. At the other extreme, in the southernmost breeding populations of Heermann’s Gull, the first-cycle molt can include all of the primaries, and sometimes it may even be complete (Howell & Wood 2004). It seems likely that these extremes reflect latitude, sunlight intensity, time of fledging, and food. Thus, the largely unpigmented plumage of a juvenile Glaucous Gull, grown in late summer from round-the-clock feeding of rich summer food, is not exposed to intense sunlight at high latitude, and it doesn’t get worn or need to be replaced. But sometimes even the  all-dark plumage of a juvenile Heermann’s Gull, grown in early summer from an unpredictable food supply in waters prone to El Niño events, may not be enough to protect it under an intense tropical sun.

=============================================

In their first winter, Heermann’s Gullls typically molt only some head and body feathers, and sometimes upperwing coverts. Some individuals of the southernmost populations, however, have an extensive molt that might even be complete on occasion. This individual has undergone an eccentric primary molt: the outer two primaries are still growing, and only the relatively protected innermost primary is a juvenile feather.

Photo caption p149 showing a wing flapping Heermann’s Gull, Nayarit, Mexico, January 22nd, 2007 (Steve N.G. Howell).

Heermann's Gull heermannii PB2 moult (2CY), July 09 2018, Pismo Beach, California USA. Picture: Alex Abela.

Double moult wave.