Great stuff

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Cristian Mihai
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Great stuff

Post by Cristian Mihai » Sun Apr 01, 2012 4:47 am

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Re: Great stuff

Post by marsmuusse » Mon Apr 09, 2012 11:44 am

Most of the discussion moved to:

I replied to Mark:

After some time looking closer at returning LBBG in N Europe in spring and summer, my opinion is that moult sequences and moult timing in LBBG taxa are sometimes hard to pin down in fixed categories. Main problem is that we have "single point" observations, and reconstructing the complete process of what may have been going on on the wintering grounds often is pure speculation. Therefore great compliments to Mark, who spend much time on this single individual, nicely illustrates the process by these images. I corresponded a few times with Mark, and maybe part of this is interesting to others as well, so I copy some text below of what we have discussed (hope you agree, Mark, and I now added a few links as well). Most of us in Europe use a slightly different ageing system; we use calendar year + month to age birds, e.g. 3cy January or adult March. But I guess you will understand what I mean. The text below, dealing with Mark's LBBGs has been written in January, in fact before we knew how this moult would develop. Mark asked if there are differences between LBBG taxa in Europe, which I studied for a while here in the Netherlands. On forehand, I like to stress it is much easier to get insight of 'ordinary moult sequences and moult timing' from observations of Herring Gulls, than it is from Lesser Black-backeds, which have a bewildering variety of strategies. Also michahellis Yellow-legged Gull is known to have an extensive post-juvenile moult, much hampering ageing of feathers in subsequent generation. My reply to Mark:

"To get an idea of feather generations in 3cy LBBG, it is necessary to consider the moult in previous years. Classic graellsii from the U.K. has a moult schedule not too different from Herring Gulls. The post-juvenile moult in 1st winter normally includes the scapular region, and that's it for bulk of the birds. Examples to show the similar moult extent between HG and LBBG:
Typical Herring Gull, 2cy March:
Typical U.K. graellsii, 2cy March:
Typical U.K. graellsii, 2cy March:

Next will be a complete moult starting in spring, including all primaries and all wing-coverts. Example:

In the covert panel, the first phase of this complete moult sequence "normally" shows: a moult wave starting from the upper tertials (tt); a moult wave starting in the inner median coverts (mc), a moult wave starting in the inner greater coverts (gc). This is probably best illustrated again by Herring Gulls. Examples:
Herring Gull 2cy May, note that covert moult also start from two loci, and tertial moult start from the upper tertials downwards:
Herring Gull 2cy June:
Herring Gull 2cy April-May:

When this complete moult approaches the last stage, normally by mid- September, there will be no old primaries left. The secondary gap closes at about S16-S17, and by this time the last 2-3 primaries have to grow a few inches. From mid-September onwards, it is not unusual to find birds in a "partial autumn moult" (which is not described by any literature I think). Again, the wing-coverts which were moulted early in the complete moult a few months ago are replaced (mc and innermost gc and often randomly some lower lesser coverts), and often the pattern is more adult-like (but not necessarily). Also the upper 2-3 tertials are replaced in this partial autumn moult. This partial autumn moult may last into late-October, but then graellsii is ready for its "2nd winter plumage".
Note fresh upper tertials here in 2cy October graellsii:
Note fresh upper tertials and inner gc here in 2cy October graellsii:
Note fresh upper tertials, inner gc and most mc here in 2cy September graellsii:

Ideally, of course, such partial autumn moult should be described in birds with limited post-juvenile moult. We have such birds: Herring Gulls! They show no post-juvenile moult in coverts and tertials, they show first stage of complete moult to start in mc, inner gc and upper tt. Now, if they replace these coverts and upper tertials again in autumn, we may pretty sure dealing with a next generation of feathers. Examples:
Note fresh upper tertials here in 2cy October argenteus:
Note growing upper tertials and missing of complete mc row here in 2cy October argenteus:

So, in analogy of Herring Gulls, we may assume typical graellsii Lesser Black-backed Gulls to show a similar moult schedule, even when we only have 'single point' observations (Herrings, on the contrary, remain in our area year-round and are easily followed throughout the process).

Intermedius LBBG is a bit of an obscure bird. You may find birds following the exact sequence outlined above for graellsii. But a substantial portion has another strategy (and a small portion of graellsii as well). Intermedius retain juvenile plumage for quite long as 1cy birds, only replacing single scapulars by December. Examples:
Scandinavian intermedius, 1cy December replaced single scapulars: ... cydec.html
Scandinavian intermedius, 1cy December still completely juvenile:

But then, when daylight period increases, already by March they start replacing wing-coverts, often in the ordinary sequence as observed in the complete moult (first mc, inner gc, outermost gc and two waves growing to each other, in the mean time many of the lesser coverts. Tertials are replaced simultaneously from TT1 downwards, but often TT6 remains juvenile. The exact extent of this process is very variable between individuals; some just replace several medians, inner greaters and two tertials; while other birds regrow the complete covert panel. They then also include most tertials as a rule. These birds look fresh when they arrive at my local patch, by May, and the extensive moulting birds very often show new rectrices as well, and the most extensive birds may have replaced secondaries.
Scandinavian intermedius, 2cy early March in active moult, note combination of missing coverts, fresh coverts and fresh upper tertials: ... cymar.html
Scandinavian intermedius, 2cy June after extensive spring moult:
Scandinavian intermedius, 2cy June after extensive spring moult:

Note however: they still do not moult any of the primaries; hence this winter moult should not be regarded as a classic complete moult, just shifted in time to an earlier stage. This sequence is different! These very extensive birds are not very keen starting the complete moult early in the season, however, during summer months they replace all the primaries (and tail and secondaries when this was not done on the wintering grounds). They also replace wing-coverts, but the exact sequence is extremely difficult to reconstruct: in mid-summer you may see very worn juvenile feathers, slightly worn 2nd gen coverts from the wintering grounds (about 2 months old), missing feathers, and very fresh recently replaced 2nd gen feathers. By mid-September it becomes almost impossible to be certain about exact feather generations in such intermedius birds. Examples:
Scandinavian intermedius, 2cy October:
Scandinavian intermedius, 2cy October probably showing 3rd generation rectrices:
Scandinavian intermedius, 2cy September, active primary moult, very old (juvenile?) feathers in the carpal edge, worn 2nd gen central tt, fresh 2nd gen central gc, growing central mc (3rd gen?): ... ysept.html

More or less the same cycle goes on for 3cy Herring Gull (and in general also in 3cy graellsii birds - and maybe older birds as well), although the partial autumn moult is difficult to observe as all feathers are identically patterned once the get an adult-like pattern (or better, not patterned, ie adult). Despite the "classic moult strategy" in many graellsii, we also see many 3cy spring LBBGs in N Europe, showing fresh rectrices replaced on the wintering grounds and birds showing more extensive moult, now including secondaries and even primaries. This also occurs in western type graellsii LBBG. I will not completely copy our findings, if you are interested, just read the BW2005 article:
Here a few links to example birds to show the increasing scale of feather tracts included in the winter moult:

Typical U.K. graellsii, 3cy February; the fresh 3rd gen coverts and tertials from the partial autumn moult still stand out between older 2nd gen coverts, but all flight feathers are typically 2nd gen:
And another typical U.K. graellsii, 3cy March:
And another typical U.K. graellsii, 3cy March:
And another typical U.K. graellsii, 3cy May:

Examples of replaced rectrices on the wintering grounds:

Examples of replaced rectrices & secondaries on the wintering grounds:

Examples of replaced rectrices, secondaries & primaries on the wintering grounds: ... -gull.html

Recently we are making just a bit of progress in collecting information on moult sequences and strategies of eastern LBBG (nominate fuscus and heuglini, for which many thanks to Amir Ben Dov from Israel for fuscus). Moult in multiple loci seems quite common in these taxa, and especially heuglini may return in N Europe in spring with virtually all possible combinations of juvenile-replaced feathers. Just some illustrations:
Heuglini 2cy June, only scapulars replaced, otherwise juvenile:
Heuglini 2cy June, coverts and tertials replaced, but flight feathers juvenile:
Heuglini 2cy June, coverts, tertials and some rectrices replaced, but primaries and secondaries juvenile: ... une01.html
Heuglini 2cy June, extensive moult, including rectrices and secondaries, and also ........ outer (!) primaries:
Heuglini 2cy June, extensive moult, including most primaries, but central primaries juvenile (nice illustration what happens when two moult waves are involved?):
Heuglini 2cy June, extensive moult, including rectrices and outer secondaries, and inner primaries, much like an ordinary complete moult sequence: ... ini14.html
Heuglini 2cy June, extensive moult, including all flight feathers: ... ini10.html

And here an example of typical 2cy spring nominate fuscus after its extensive winter moult:
fuscus 2cy May: ... ay2cy.html

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