As the immediate problem for the beginner will be to identify the species, the idea of ageing and sexing may seem like an unnecessary complication.
With many species, however, ageing may be an important first step to identification and in some cases it may, at a stroke, eliminate several confusion species.
for example, many of the old text books illustrate only summer and winter adults.
The fact is that many waders have an equally distinct juvenile plumage.
Is it any wonder that confusion arises when, in many cases, the most commonly occuring plumage type is not even illustrated?
Tied in with ageing and sexing is, of course, moult.
As a general rule, most adult birds have two moults a year, a body moult in late winter-spring and a complete moult in late summer.
This simple knowledge of moult times is surprisingly useful and associated with this, so too is the correct use of ageing terminology to ensure that we are all speaking the same language.
A bird's first feathers, after it leaves the nest, are called "juvenile plumage", and in most species this is retained until late summer, when there is a body molt juvenile is then replaced by "first winter" plumage.
In most small passerines, this is basically adult plumage, but many species take longer to reach maturity and they go through a whole sequence of immature plumages before reaching adulthood.
As a general rule, the bigger the bird, the longer it takes to reach maturity.
Thus, a black headed gull has a distinct first winter plumage, but, in the following spring, there is another body moult, after which "first summer" plumage is acquired, then, in late summer, when just over one year old, it has its first complete moult, and, thereafter, it is adult.
The common gull, on the other hand, takes two years to reach maturity, so first summer is followd by second winter and then second summer before adulthood is reached.
It may be worth remembering, however, that, if any feathers are lost, they may be replaced by feathers of the subsequent plumage type.
First winter and first summer plumages are often lumped together as first years.
Similarly, second winter and second summer may be lumped as second year, and so on.
Most passerines moult out of juvenile plumage before they migrate in autumn, so late August-October migrants are largely in first winter plumage, which in many cases is not safely separable from adult winter in the field.
On the other hand, many species migrate in juvenile plumage and many do not moult to first winter until they reach their winter quaters.
Others may start to acquire their first winter feathering while still on migration, so that they have a patchy mixture of juvenile and first winter plumages.
It should be remembered that, compared with the adults, autumn juveniles are usually very neat and immaculate as their plumage is fresh, in many species, the contemporary late summer adults look very worn and tatty in comparison.
Some large species, such as many large eagles, undergo an almost continuous moult so that several different ages of feathers may be present at any one time.
In such cases it is often sensible to age the bird by calendar year.
The year in which the bird was hatched is termed the first calendar year, the second calendar year starting on 1 January of the next year, and so on.
One particularly important point to remember is that immature simply means 'not mature' and so can be applied to any bird that is not an adult.
Thus, juvenile,first winter and first summer plumages are all immature plumages, but many observers confuse immature with juvenile.
You should try to avoid using the term immature in relation to any one individual bird, as it is usually possible to be more accurate.
Similarly, sub adult is also to be avoided if possible, as again more accurate ageing can usually be determined.
When indentifying birds and assessing ageing, bear in mind the effects of wear, abrasion and bleaching.
Old feathers wear and fade and significant plumage features can disappear though wear, while some species alter plumage tone.
Immature gulls are notoriously prone to wear and bleaching, and may look particularly tatty and faded in summer, when theit wing and tail feathers are nearly a year old.
Some species have only one complete moult a year, in late summer, and their summer appearance is the result of feather wear...
Test your knowlege, this GULL is First or second year????? And the species is ........GULL????