Thanks to the work of PRBO Conservation Science, I have been able to put together this web page of known age Western Gulls. PRBO has been banding Western Gulls on the Farallon Islands, San Francisco County, California for a long time. Apart from the standard metal band, PRBO has been using a color band to designate the cohort, the year they were hatched. So if you can see a color band, you can identify when that particular bird hatched on the Farallons, and assuming a mid-June hatching period then you can estimate the age of the bird. There are a lot of gaps left here, and the quality of the photos varies, but it's a start. As I get more photos I will post them. Unless noted otherwise, these birds were photographed in Half Moon Bay, San Mateo County, California....as the gull flies, not all that far from the Farallons. One of the birds in this set was actually banded on Alcatraz Island, San Francisco County.
Only one photo is shown of each individual, and each bird is labeled above the photo.
For a paper on dispersal of Farallon Western Gulls, click here. For more info on PRBO's work, go to www.prbo.org.
Jump to Second Cycle, Third Cycle, Definitive (Adult) cycle.
5 months old - Banded Summer 03 as nestling, photo Nov. 24, 2003. Upperparts have largely been molted out of the juvenal plumage but a few scattered juvenal feathers remain, juvenal coverts still quite fresh.
5 months old - Banded Summer 03 as nestling, photo Nov. 26, 2003. Upperparts have already been molted out of the juvenal plumage, juvenal coverts still quite fresh.
6 months old - Banded Summer 03, on Alcatraz Island as nestling, photo Dec 3, 2003. Upperparts have already been molted out of the juvenal plumage.
6 months old - Banded Summer 03 as nestling, photo Dec 3, 2003. Band number 2406-13236. Upperparts have already been molted out of the juvenal plumage, retains juv lowermost scapulars (just above tertials).
6 months old - Banded summer 2005, photo December 24, 2005. Photo © Jeff Poklen, Rio del Mar, Santa Cruz Co, California. This is an individual with a deformed bill, that is obvious from the form of the bill but unexpectedly the color of the bill is also unusual particularly for a gull as young as this which would be expected to show a largely dark bill.
6 months old. Banded summer 2005, photo December 29, 2005. Upperparts new, but note longest scapulars (partially hidden) are retained juvenile. Next row up look grayish and more adult like, perhaps these were molted in later than the rest of the mantle, but were part of the same molt?
6 months old. Banded summer 2006, photographed Dec. 31, 2006. Classic gray toned new body feathering contrasting with browner wings.
8 months old - Banded Summer 04 as nestling, photo Feb. 21, 05. Retains juvenal wings and tail as well as lowermost scapulars. Upperparts first basic (formative) plumage.
9 months old - Banded Summer 04 as nestling, photo March 21, 05. Retains juvenal wings and tail as well as lowe scapulars. Either retained or early molted central scapulars, otherwise head, neck and upperparts not juvenal. Note more pointed primary tips, and more slender primary shape classic of juveniles.
1yr, 2mo - Banded summer 04 as nestling - photo Aug. 9, 2005. Nearly finished transition from first plumage cycle to second plumage cycle. Primaries still growing.
1 yr, 4 months old - Banded summer 2003, photo October 29, 2004. Photo © Jeff Poklen, Rio del Mar, Santa Cruz Co, California. Note how far advanced this bird is compared to the previous one only a couple of months younger. Median coverts appear to have been replaced after the second prebasic molt.
1yr, 6 mo - Banded Summer 02 as nestling - photo Dec 10, 2003. Band Number 2406-12448. Second cycle wings show contrastingly more adult median coverts. In this bird, broken up by older retained brown median coverts. This suggests that the gray medians have been molted in posterior to the second prebasic molt of the previous summer.
1 yr, 6 months old - Banded summer 2004, photo December 24, 2005. Photo © Jeff Poklen, Capitola, Santa Cruz Co, California.
1 yr, 6 months old - Banded summer 2004, photo December 24, 2005. Photo © Jeff Poklen, Capitola, Santa Cruz Co, California.
1 yr, 6 months - Banded summer 2004 as nestling, photo December 29, 2005.
1 year, 6 months. Banded summer of 2004, photo taken February 11, 2006. Not the best angle, but shows some gray on median coverts, entirely black tail, white rump etc.
1 year, 6 months. Banded summer of 2004, photo February 17, 2006. This sharply contrasting yellowish bill with black tip is a common pattern which is seen at this age.
1yr, 8 mo - Banded Summer 03 as nestling - photo Feb. 12, 2005. Slightly more advanced than following bird, of same age, this one showing more extensive pink on bill and more adult like median coverts.
1yr, 8 mo - Banded Summer 03 as nestling - photo Feb. 19, 2005. Perhaps the classic pattern for a second cycle bird, with brownish wings (coverts) and gray mantle. Not so common at this age is the extensively blackish bill, Western tends to show a yellow base by now.
1 yr, 10 months old - Banded summer 2002, photo April 30, 2004. Photo © Jeff Poklen, Rio del Mar, Santa Cruz Co, California. It is interesting to see the variation in bill color, compared to the previous individual only 2.5 months younger. Perhaps this is individual variation, perhaps it is hormonal based color change during the breeding season.
2 years, 0 months. Banded summer of 2004, photo taken June 27, 2006. This is an interesting photo as this bird is undergoing the molt that takes it from the second to the third cycle. The mantle is entirely gray and new, and the wing coverts are being quickly replaced with the medians actively being molted in the photo. The visible primaries, secondaries and greater coverts are still from the second cycle. But by the end of the summer this individual will look much more adult like than it does currently. Not to me one of the major lessons of this photo is in the head and bill. These look "advanced" for a second cycle bird, but this bird was photographed in the summer. This is key, as this photo suggests that summer second cycle birds show more mature bill colors than they do in the winter, even more so than winter third cycle bills. It makes sense that as these immature birds are undergoing hormonal shifts, even if they are not breeding yet, they would show a tendency for "breeding color" bills in the summer, less so in the winter. The scruffy look to the head suggests those feathers have not been molted yet, so they are worn and faded, therefore entirely white.
2 years, 3 months. Banded summer of 2004, photo taken September 14, 2006. This individual is pretty adult like, not showing obvious black on the tail. I also can't detect any brown wash on the coverts. The most obviously immature feature is the gray marking on the head. Interestingly the bill shows little dark, perhaps it is still has not changed to a winter type bill color (see above photo)? It is still in active wing molt, growing in the outer primaries, this is why it looks short on the rear.
2 years, 6 months. Banded summer of 2004, photo taken December 11, 2006. A very adult-like individual, perhaps lacking black on tail although it is impossible to say for sure in this view. The immature features that can be seen are the gray clouding on the head, extensive dark on bill tip and some brown wash on inner greater coverts. As well the primary tips are smaller than on adults.
2 years, 6 months. Banded summer of 2003, photo December 29, 2005. Note that while generally adult like, at this age during winter Western Gulls can show extensive dark markings on the head. Since this is a Farallon bird, well away from the hybrid zone, the dark head markings should be considered an effect of age, not genes from Glaucous-winged Gull.
2 years and 6 months. Banded summer of 2004, photo taken Dec. 25, 2006. Another largely adult like bird, with a hint of brown wash on coverts, a well streaked head and some telltale black on the tail.
2 years, 6.5 months. Banded summer of 2003, photo January 3, 2006. The bright yellow bill with a dark tip is a common pattern seen on third cycle Western Gulls.
2 years, 7 months old, banded summer 2003, photographed January 17, 2006. Again, showing the common yellow bill with black tip pattern.
2 yr, 8 mo - Banded Summer 02 as nestling - photo Feb. 12, 2005. Basically adult like, but look at retained older lesser coverts, black on tail, lack of mirror on outer primary, lack of large primary tips, extensive black on bill.
2 yr, 9 mo - Banded Summer 02 as nestling - photo March 21, 2005. Basically adult like, but look at brownish tone to primaries and the lack of white tips, as well as the extensive black in tail. Other signs of immaturity include dark on bill, and brownish tone to wing coverts and tertials.
3 years old. Banded summer of 2003, photo taken June 28, 2006. This bird retains the third cycle wings and tail and will be molting them shortly. It has a new back and appears to be molting coverts. Note how this bird and the March one above show bright (adult like) bill colors. It seems that the bills become more adult like in summer, and then gain dark again in the non-breeding season in immature birds.
3 years, 7 months, banded summer 2002, photo January 17, 2006. So this bird is in its fourth cycle, its first true adult plumage. Interestingly it shows no streaking on head, or dark on bill.
3 years, 7 months, banded summer 2002. Photo February 2, 2006. So this bird is in its fourth cycle, its first true adult plumage. Interestingly it shows no streaking on head, or dark on bill. Jeff Poklen photo - Santa Cruz county.
4 years old. Banded summer of 01, photo June 10, 2005. No sign of immaturity, primary tips worn off as primaries are quite worn in mid June.
4 years, 7 months. Banded 2001, photo January 16, 2006. This individual has some dusky on the head, interesting, so at least some adult birds breeding well away from the hybrid zone do show streaking on the head. Photo by Jeff Poklen, Santa Cruz County.
4 years, 8 months. Banded summer of 2001, photo taken February 11, 2006.
5 years, 8 months. Banded summer of 2000, photo taken February 17, 2006. Classic adult lacking dark on head, and on bill.
6 years, 8 months. Banded summer of 1998, photo Feb.. 19, 2005. No sign of immaturity. This bird was photographed in the middle of winter. Pure Western Gulls in mid-winter should show no dark on the head if fully mature, dark streaking would suggest hybridization with Glaucous-winged Gull. Since we know where this gull was hatched, Farallon Islands, California, we know it is well outside the hybrid zone. The standards for occidentalis Western Gulls should be these birds.
