Waders month by month

Introduction

Perhaps this is an over-ambitious idea! It is an attempt to document waders I’ve seen in Malaysia on a month-by-month basis, in an effort to show and perhaps unravel some of the complexities of wader plumages.

Before I get into the species accounts, which I will add gradually as and when the inspiration strikes, here’s a guide to how wader plumages progress through the year.

A Simple (hopefully!) Guide to Moult in Waders

Waders breeding in the northern hemishere and spending the non-breeding season south of the Equator follow a regular pattern of moult, enabling them to maintain their plumage in a condition which keeps them warm in the cold, cool in the heat, and makes their extraordinary long-distance flights possible. Moult sequence and timing is tied into their migrations, and is therefore largely predictable. Attempting to understand moult and the sequence of plumages a bird goes through is an interesting study in its own right, but here I am describing it mainly as an aid to identification.

Juvenile Plumage

Waders are covered in down when they hatch, and their first set of feathers, which develop in the weeks after hatching, is termed ‘juvenile plumage’. The entire first set of feathers develops more or less at the same time, so is of uniform age.

Juvenile feathers are smaller than adults’, and because of this, and the fact that they are all of uniform age, they typically look neat and “well-arranged.”

They are usually highly patterned compared to adult feathers, and often have pale edges or ‘notches’. However, juvenile feathers are not as robust as adult feathers (a development trade-off: strength is sacrificed for faster growth), so they quickly abrade or ‘wear’ when exposed to the elements.

The effects of feather wear on a single juvenile Curlew Sandpiper. In ‘fresh’ plumage, the pale buff and peach feather edges are prominent. Pale areas lack pigment, so they abrade faster than darker (pigmented) areas. As the pale areas wear away, the bird begins to look darker and it loses some of the bright tones.

It’s rather easy to spot juveniles in flight (in early autumn). All the flight feathers are the same age, forming a nice neat trailing edge to the wing, with no gaps caused by moulted or growing feathers.

First winter/first non-breeding/formative Plumage

Juveniles of most migratory wader species undergo a body moult in their first autumn into a plumage variously known as “first winter”, “first non-breeding” or “formative” plumage. This takes place roughly in Sep – Nov.

During this moult, the old juvenile flight and tail feathers, and usually at least a number of wing coverts are NOT replaced.

These birds now look similar to adults except for some retained juvenile wing coverts and perhaps scapulars (which are now very worn), flight and tail feathers.

This bird is still mostly in juvenile plumage (very faded and worn), but there are some fresh grey “first non-breeding” scapulars.

This one, on the other hand, has completed its moult into first non-breeding plumage. Note the darker, more patterned juvenile median and lesser coverts. Lesser coverts, because they are protected by the overlaying scapulars, tend to abrade more slowly than other wing feathers, and perhaps for that reason, tend to be the last ones replaced ( sometimes not until the following moult). Note: Each individual follows its own moult schedule within the broader timeframe. These two birds were photographed at the same place on the same day.

First summer/first breeding/first alternate Plumage

From about Febraury onwards, last year’s hatched birds undergo another body moult.

This is usually a rather drawn-out process. Since the birds are not sexually mature, the urge to return to the breeding grounds is weak, as are the hormonal impulses to assume breeding colours. Many waders take the equivalent of a ‘gap year’, not performing a full migration, but ‘hanging out on the beach’ somewhere on or near the non-breeding grounds.

First-breeding plumage is usually a combination of weakly coloured and patterned breeding plumage feathers and increasingly worn and ragged first non-breeding and juvenile feathers.

The extent to which these birds assume breeding plumage probably depends on how active their hormones are. Birds staying on in Malaysia may look just like worn non-breeding adults, whereas others, which migrate some of the way northwards, develop more breeding plumage colours (see this first breeding Curlew Sandpiper in Japan for example).

An ‘oversummering’ flock of waders at Kapar in late June.The Common Redshank on the right has a combination of weakly-patterened breeding head and flank feathers, and excessively worn and bleached scapulars. This is typical of first breeding plumage. Sometimes, feathers wear away so much that only the shaft remains, or they may drop out altogether. When this happens, the white bases of the feathers beneath, which are normally hidden, show up as odd whitish patches on the upperparts, which can cause confusion!

Midsummer madness! Extreme wear on this first breeding plumage Greater Sand Plover has caused it to show a white collar.

Although waders aren’t “supposed” to moult their flight feathers till autumn, some non-breeders begin to do so as early as June. In this photo, note the older plain, dull outer primaries and fresh, richly coloured and patterned inner ones. Although I’ve assumed that all oversummering birds are first years, with larger species like godwits, Whimbrels and curlews, it may take 2-3 years before they reach sexual maturity, so some of these might be in “2nd summer” plumage.

Adult winter/adult non-breeding/basic Plumage

All waders except juveniles (of most species) undergo a complete moult in the autumn. This is the first time they have replaced their flight and tail feathers for 12 months (or more, in the case of last year’s juveniles).

Some species, like Greater Sand Plover, complete this moult before they leave the breeding area, but most complete it during southward migration.

Although all feathers are replaced, this doesn’t happen at the same time, so there are always small differences between ages of feathers. Also, because adult feathers are larger than juvenile ones, they never seem to fit into such neatly arranged rows as on juveniles.

Compare this adult to the first winter Curlew Sandpiper further up this post. The larger scapulars tend to cover more of the coverts, and the feather arrangement looks more ‘messy’, as if there are too many feathers for the space available.

In autumn, adults can easily be told from juveniles by the uneven trailing edge of the wing, caused by new feathers growing out and the presence of unmoulted, ragged-ended old feathers.

Adult summer/adult breeding/alternate Plumage

Breeding plumage is achieved by a body moult in spring, usually during northward migration.

Surprisingly, the rich, brightly coloured breeding colours are also a product of feather wear.

Fresh breeding plumage feathers have broad pale edges to most feathers. Note that most of the wing feathers are still the old non-breeding feathers. A limited number of these, especially tertials and greater coverts (perhaps more as the bird gets older), are replaced by more brightly coloured and patterned feathers.

As the feathers are exposed to the elements, the paler edges wear away.

By the time the bird has completed a long northward journey, the feather edges have worn away completely, producing an intensely coloured plumage. Males of most species  are more brightly coloured than females (well-known exceptions are phalaropes and painted-snipes).

A fresh breeding-plumaged Curlew Sandpiper in early April.

Once a bird has entered adulthood, it repeats the twice annual moult cycle – a complete moult in autumn and body moult in spring. The way I remember this is All in Autumn, Some in Spring!

Practice!

That’s a lot to take in at one sitting, and if this is the first time you’re learning about wader moult, then you’ll probably need to refer back to it a few times. But, once you feel you’ve more or less got the basics, you may want to try testing yourself by working out the ages of the birds in the photos below (answers in the Replies!). Notes the dates – they’re there to help you!

1.Broad-billed Sandpipers a. left b. right

2. a. Curlew Sandpiper (back) b. Red-necked Stint (front)

3. Curlew Sandpiper

4. Lesser Sand Plover

5. Lesser Sand Plover

6. Terek Sandpiper

7. Terek Sandpiper

8. Eurasian Curlews a. front b. back

9. Nordmann’s Greenshank

10. Nordmann’s Greenshank

Advertisement