Silver Gull – 1st immature breeding.

By Birding-Aus, on June 5th, 2011

G’day everyone,

This link is to a picture I took of 2 Silver Gulls. http://bit.ly/lYaTec

Using HANZAB as a guide, it has the bird on the left as a 1st immature breeding, and the bird on the right as an adult in breeding plumage. My question is does anyone know if the bird on the left will actually breed whilst in this plumage, or will it wait until it gets its full adult breeding plumage before it breeds? (Could they be the birds that are referred to on page 534 where it says ‘Gulls breeding after first peak [breeding] mainly inexperienced birds’?)

And why is it called 1st immature breeding plumage when it looks more like the 1st immature non-breeding rather than the adult breeding plumage?

Regards, Mark

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"Mark and Amanda Young"

June 6, 2011 at 7:39 pm

G’day David,

Thanks for the awesomely elaborate response. You’ve answered my questions and provided me with much more. Until your email I never realised that describing moults and plumage was such a complicated process.

I guess what was confusing me a little is that I assumed that where birds plumage are referred to as being 1st and 2nd years, I was sub consciously thinking of a calendar year rather than the first year of the birds life. And if I’ve read what you’re saying correctly, these years contain cycles that aren’t necessarily related to a calendar year as we see it as these birds in some cases may breed most of the year or all year round.

I think I erred this way because I was thinking of birds that have a definite breeding time period every calendar year, and what I’ve now learned is that their cycle of moult, can be expected at certain times of the year. So I guess in those cases them you could reconcile the 1st and 2nd year plumages with the calendar year, but not so with Silver Gulls in Sydney.

The background about Dwight and H@P and the differences in the models explain so much. I was conversing with someone in the US a few months ago about birds over there and he tended to use terms I hadn’t heard before like, winter and summer plumage, and referring to eclipse plumage as alternate plumage, and juvenile as basic plumage. I thought at the time that it must be what they say over there, but I wonder now if his information was based on the H@P model?

Regards,

Mark

Sent: Monday, 6 June 2011 11:08 AM

Hi Mark,

Silver Gull is not likely to breed in “1st immature breeding plumage”. The explanations to this and your other questions are both technical and messy, and likely to bore most readers (hint).

Plumages are introduced by moults and there is a sequence of moults and plumages. These follow complicated patterns and different groups of species do it slightly different ways. To understand these patterns ornithologists have developed conceptual models and accompanying terminology. There is more than one model, and no model is correct, but some are better (or more accurate) than others. Since more accurate means more complicated it also means less general appeal.

There are two general models, that of Dwight (1900) and Humphrey and Parkes (1959). Both have variations that I’ll get to later. they use different terminology.

Starting with the growth of the natal down, all birds moult from one plumage to the next. Note that a moult includes the shedding of old feathers and the growing of new ones. Each feather can be said to belong to a ‘generation’ that is defined by the moult it grew in. Each moult can be ‘complete’ (i.e. involving all of the feathers) or partial. Partial moults typically include the contour feathers (i.e. head, body, coverts) and omit the flight feathers, but it varies widely. The two most frequent patterns are birds that have one complete moult a year, and birds that have one complete and one partial moult each year (but in some species the cycle is more than a year and in a few it is less than a year). Gulls have two moults per cycle. Once a bird is already adult, a complete moult leads to an adult plumage of a single generation, but a partial moult leads to an adult plumage comprised of two generations of feathers.

Dwight linked plumages to the breeding cycle. Thus he said that a bird with two moults per year has a breeding plumage and a non-breeding plumage. It turns out that most birds with two moults per cycle have a partial moult before they breed and a complete moult after they breed. Therefore adult birds wearing one complete generation of feathers are said to be in “adult non-breeding plumage” and those with two generations (tail and primaries grown in a complete moult and then body feathers grown in a subsequent partial moult) are said to be in “adult breeding plumage”. Projecting this terminology back to pre-adult feathers you get “immature non-breeding plumage” and “immature breeding plumage”. It is not intended to mean they breed in immature breeding plumage”, just that this plumage is in the same stage of the cycle as sexually mature birds in “adult breeding plumages”. Where there is more than one cycle of immature plumages they are modified with sequential numbering: 1st immature non-breeding, 1st immature breeding, 2nd imm non-breeding, etc.

Dwight also thought that of moults as points between plumages. Thus he named the moults ‘post breeding moult’ and ‘pre-breeding moult’

Dwight’s model has some inherent problems. Others recognised that ‘breeding’ and ‘non-breeding’ terms are a problem and suggested ‘summer’ and ‘winter’ and ‘eclipse’. This replaces one problem with another, since moults evolved to renew feathers, not signify seasons.

Humphrey and Parkes sort to make a model that reflects the evolutionary origins of moults in birds. They introduced a terminology that removed the association between breeding, sexual maturity, seasons and so forth with plumages and moults. Therefore the terminology is novel and many people find it unappealing. It goes like this. The single generation of feathers obtained by a complete moult is termed the ‘basic plumage’ and the plumage of two generations created by a partial moult is called an ‘alternate plumage’. Instead of referring to adults, they used ‘definitive basic plumage’ and ‘definitive alternate plumage’ for birds that had reached the final stage of plumage. For younger birds they did not use immature but still numbered the plumages sequentially: 1st basic, 1st alternate, 2nd basic, 2nd alternate… definitive basic, definitive alternate. Thus the model allows for sexually mature birds to breed in non-definitive (so called immature) plumage and for sexually immature birds and post-breeding birds to be in definitive plumage without breeding. The moults are defined by the plumages they introduce, never the ones they replace: 1st pre-basic, 1st pre-alternate.

Superficially it seems like just a change of names, but in reality Dwight’s model does not apply to all cases and can be very muddled. The semantics allows the mind to understand the patterns and classify each case – the better the semantics the more consistency. The original Humphrey and Parkes model had a major flaw which has been corrected since HANZAB III was written, but the required adjustment to make the model right is unfortunately very messy and confusing.

Dwight was adopted world wide. Humphrey and Parkes supplanted it in the new world, but did not take off in the old world. The Birds of the Western Palearctic (BWP) used a system modified from Dwight. Australian field guides and literature have also followed the Dwight system. HANZAB followed BWP, but in the text it also named plumages and moults according to Humphrey and Parkes (because it is better). So you will see in the plumages text for Silver Gull in HANZAB that your birds are labelled in brackets as first alternate and definitive alternate, with no prediction or reference to their sexual maturity or breeding condition, or the time of year.

The reference on page 534 is to birds that are sexually mature but have not had much nesting experience. Such birds are likely to be in “definitive alternate plumage”. but you can’t predict this just from the knowledge that they are breeding.

David James, Sydney burunglaut07@yahoo.com ==============================

Sent: Sunday, 5 June 2011 10:15 PM

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David James

June 6, 2011 at 11:08 am

Hi Mark, Silver Gull is not likely to breed in “1st immature breeding plumage”. The explanations to this and your other questions are both technical and messy, and likely to bore most readers (hint). Plumages are introduced by moults and there is a sequence of moults and plumages. These follow complicated patterns and different groups of species do it slightly different ways. To understand these patterns ornithologists have developed conceptual models and accompanying terminology. There is more than one model, and no model is correct, but some are better (or more accurate) than others. Since more accurate means more complicated it also means less general appeal. Starting with the growth of the natal down, all birds moult from one plumage to the next. Note that a moult includes the shedding of old feathers and the growing of new ones. Each feather can be said to belong to a ‘generation’ that is defined by the moult it grew in. Each moult can be ‘complete’ (i.e. involving all of the feathers) or partial. Partial moults typically include the contour feathers (i.e. head, body, coverts) and omit the flight feathers, but it varies widely. The two most frequent patterns are birds that have one complete moult a year, and birds that have one complete and one partial moult each year (but in some species the cycle is more than a year and in a few it is less than a year). Gulls have two moults per cycle. Once a bird is already adult, a complete moult leads to an adult plumage of a single generation, but a partial moult leads to an adult plumage comprised of two generations of feathers. Dwight linked plumages to the breeding cycle. Thus he said that a bird with two moults per year has a breeding plumage and a non-breeding plumage. It turns out that most birds with two moults per cycle have a partial moult before they breed and a complete moult after they breed. Therefore adult birds wearing one complete generation of feathers are said to be in “adult non-breeding plumage” and those with two generations (tail and primaries grown in a complete moult and then body feathers grown in a subsequent partial moult) are said to be in “adult breeding plumage”. Projecting this terminology back to pre-adult feathers you get “immature non-breeding plumage” and “immature breeding plumage”. It is not intended to mean they breed in immature breeding plumage”, just that this plumage is in the same stage of the cycle as sexually mature birds in “adult breeding plumages”. Where there is more than one cycle of immature plumages they are modified with sequential numbering: 1st immature non-breeding, 1st immature breeding, 2nd imm non-breeding, etc. Dwight also thought that of moults as points between plumages. Thus he named the moults ‘post breeding moult’ and ‘pre-breeding moult’ Dwight’s model has some inherent problems. Others recognised that ‘breeding’ and ‘non-breeding’ terms are a problem and suggested ‘summer’ and ‘winter’ and ‘eclipse’. This replaces one problem with another, since moults evolved to renew feathers, not signify seasons. Humphrey and Parkes sort to make a model that reflects the evolutionary origins of moults in birds. They introduced a terminology that removed the association between breeding, sexual maturity, seasons and so forth with plumages and moults. Therefore the terminology is novel and many people find it unappealing. It goes like this. The single generation of feathers obtained by a complete moult is termed the ‘basic plumage’ and the plumage of two generations created by a partial moult is called an ‘alternate plumage’. Instead of referring to adults, they used ‘definitive basic plumage’ and ‘definitive alternate plumage’ for birds that had reached the final stage of plumage. For younger birds they did not use immature but still numbered the plumages sequentially: 1st basic, 1st alternate, 2nd basic, 2nd alternate… definitive basic, definitive alternate. Thus the model allows for sexually mature birds to breed in non-definitive (so called immature) plumage and for sexually immature birds and post-breeding birds to be in definitive plumage without breeding. The moults are defined by the plumages they introduce, never the ones they replace: 1st pre-basic, 1st pre-alternate. Superficially it seems like just a change of names, but in reality Dwight’s model does not apply to all cases and can be very muddled. The semantics allows the mind to understand the patterns and classify each case – the better the semantics the more consistency. The original Humphrey and Parkes model had a major flaw which has been corrected since HANZAB III was written, but the required adjustment to make the model right is unfortunately very messy and confusing. Dwight was adopted world wide. Humphrey and Parkes supplanted it in the new world, but did not take off in the old world. The Birds of the Western Palearctic (BWP) used a system modified from Dwight. Australian field guides and literature have also followed the Dwight system. HANZAB followed BWP, but in the text it also named plumages and moults according to Humphrey and Parkes (because it is better). So you will see in the plumages text for Silver Gull in HANZAB that your birds are labelled in brackets as first alternate and definitive alternate, with no prediction or reference to their sexual maturity or breeding condition, or the time of year. The reference on page 534 is to birds that are sexually mature but have not had much nesting experience. Such birds are likely to be in “definitive alternate plumage”. but you can’t predict this just from the knowledge that they are breeding. Sent: Sunday, 5 June 2011 10:15 PM

There are two general models, that of Dwight (1900) and Humphrey and Parkes (1959). Both have variations that I’ll get to later. they use different terminology. ===============================

Birding-Aus

Silver Gull – 1st immature breeding.

2 comments to Silver Gull – 1st immature breeding.

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