Ring-billed Gull delawarensis

delawarensis Ring-billed Gull

(last update: 10-03-2014 )

Coordinators:
Keith Mueller
Amar Ayyash
Mars Muusse

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

Ring-billed Gull delawarensis BLUE TAG adult, August - October 2012 & September 2013, Rainbow Beach - Chicago, IL. Picture: Amar Ayyash.

See Amar's blog.

This male was banded after the breeding season of 2007 at the Lake Calumet colony. Fed Band number: 0734-24852 Banded as adult (hatched <2007) on November 05 2007 at Chicago, IL, USA. Sex: male.

Adult Ring-billed Gulls typically complete their prebasic molts by the end of October. Here's a series of photos documenting primary growth of a known-age RBGU taken at Rainbow Beach in Chicago, Illinois. The photos are presented in three week intervals from late August through late October.

below: Gull delawarensis adult, August 25 2012, Rainbow Beach - Chicago, IL. Picture: Amar Ayyash.

P7/-. Just two white primary tips clearly showing past the tertials on 25 August 2012.

below: Gull delawarensis adult, September 15 2012, Rainbow Beach - Chicago, IL. Picture: Amar Ayyash.

P8/-. Three primary tips showing past the tertials on 15 September 2012. P8 grew significantly in the last three weeks.

below: Gull delawarensis adult, October 06 2012, Rainbow Beach - Chicago, IL. Picture: Amar Ayyash.

P9/-. Now 4 primary tips showing beyond the tertials on 06 October 2012.

below: Gull delawarensis adult, October 26 2012, Rainbow Beach - Chicago, IL. Picture: Amar Ayyash.

Finally, the tip to P10 (black) has emerged from underneath P9. 26 October 2012. This generally concludes the prebasic molt as most of the body and flight feathers are renewed by the time P10 is fully grown.

The primaries, secondaries and rectrices are all new, crisp, feathers that will get this bird through the winter, spring and most of the next breeding season.

One thing worth noting here is that the mirrors on P10, and particularly P9, are relatively small. This may be an indication as to what an adult this young (6th cycle) should look like, but it's not uncommon for some adults to be without a mirror on P9 entirely. Are these young adult females? Also, might the choppy black markings up the inner web of P8 become "cleaner" as this bird ages? The black marks on the outermost greater primary coverts above P10 are not a sign of "subadultness" - this is an expected feature on adult Ring-billeds.

below: Gull delawarensis adult, September 22 2013, Rainbow Beach - Chicago, IL. Picture: Amar Ayyash.