It’s been so long since I was in the field, I’ve almost forgotten which end of the bins to look through. But news of Swinhoe’s Plovers returning to their wintering spot on the north coast of the island tempted me out of semi-retirement, and it was good to see some old friends.
These were wary and generally roosted and fed well away from the other waders present. No leg flags, but it was a long shot.
There were about 40 Lesser Sand Plovers. The one above is a juvenile in fresh plumage, with broad buff fringes to the scapulars and wing coverts, and a beautiful delicate peachy wash over the breast and much of the ‘face’.
Another juvenile – the same species, in the same plumage, so why does it look so different? The difference in appearance is the result of feather wear. Comparing the two profile pictures above, you can see how, on the lower bird, the broad buff fringes on the scapulars and coverts have all but worn away, and the buff wash on the breast and head is also much reduced, again as a result of wear or abrasion. The net result is a very different overall look.
An adult Lesser Sand Plover in non-breeding plumage. Note the irregular appearance of the wing coverts compared to the neat, similar-sized coverts of the juveniles. Because juvenile feathers all develop at the same time, they tend to look neat and uniform in shape and size. Adult feathers are replaced gradually as a result of moult of older feathers, so often appear haphazard and at slightly different stages of growth or wear. This is a general truth which can be applied to almost all birds, and is a helpful pointer to aging. Inexperienced observers tend to identify scruffy birds as juveniles and neat ones as adults, but it’s more often the other way around.
The close up of the upperparts of this juvenile Common Sandpiper show how feather wear affects the pale areas of the feathers. The long uppermost tertial has a serrated (jagged) edge. This is because the pale ‘notches’ between the darker spots have worn away completely. The same is beginning to happen to the inner greater coverts (the feathers which overlap the bases of the tertials).
Tereks are often tricky to age. A quick check of the visible primary tips reveals no obvious sign of moult (which would be a sure indication of an adult at this time of year), and both birds seems to be quite neat, with no obvious differences in feather age on the scapulars and coverts. However, the scapular size is a help here. Juvenile scapulars and coverts are smaller than those of adults (another reason why they appear in neat rows). The upper bird shows distinctly larger scapulars and greater coverts than the lower one. This, together with the obviously brighter bill base of the upper bird, leads me to conclude that the upper bird is an adult in non-breeding plumage, while the lower one is a juvenile (fairly well-worn).
Since almost all waders only undergo a flight and tail feather moult from their second winter onwards, any bird showing moult in the flight or tail feathers cannot be a juvenile (the only wader exception to this on Malaysian soil is Oriental Pratincole, which has a full post-juvenile moult). So these Whimbrels must be ‘adults’ ie – at least a year old.
Aging this Common Redshank should be easy by now – small, neat, evenly aged feathers, lots of pale notches, very washed out bill and leg colours – everything clearly indicates a juvenile.
Again, the bird whose head is in the centre of the frame is an obvious juvenile Common Redshank, but what about the bird immediately in front and to the left of it? Careful scrutiny of the wing coverts and tertials reveal that some – the lesser and greater coverts and tertials – are juvenile feathers. However, the bird has undergone a more or less complete post-juvenile head and body moult (including a grey block of median coverts), so it is technically in ‘first winter’ plumage. Note the washed out leg and bill colours, a strong indication that it is a young bird.
Some adults, and probably some 1st and 2nd winter birds mixed in. It’s interesting to scan the legs and see the variation in intensity of orange. As a rule of thumb, subadults show less intense colours. Some juveniles may have legs which are more yellow than orange – a potential trap for the unwary! The centre bird in the top image still shows a significant amount of worn breeding plumage, making it look much darker than the surrounding birds.
So what about this one? The washed out leg colour suggests that it is less than fully adult, yet the very worn tertial indicates that it is older than a juv/first winter. Probably, this bird is in its ‘second winter’. That is, it hatched sometime in the summer of 2011. One year old birds undergo a protracted moult over their first summer, retaining odd juvenile wing feathers, which can become extremely worn before eventually being replaced.
And I think these are first winters. Despite a few irregularities along the trailing edges of the wings, and an apparently still growing tail feather on the further bird, I don’t see any sign of two age classes of feathers which might indicate that they are older. Further more, I think I can see that the retained wing coverts are juvenile-patterned. If they are first winter birds, it’s interesting that the brown cast over the tail evident on the juvenile above is absent – perhaps it’s a bloom that wears off with age.
Another interesting thing is the apparent different pattern on the tail feathers of these two birds. The further bird has simple barred tail feathers; the nearer one seems to have dark subterminal fringes on the tail feathers. Is this just individual variation or is it more significant?
The waders have to constantly be on the alert for threats (apart from me!). Here are some I saw in just a few short hours.
This subadult White-bellied Sea-eagle came down to ‘buzz’ the roosting flock. They wouldn’t normally take a healthy wader, but will routinely flush the waders to see if there’s an injured bird among them which they might have a chance of catching.
Feral dogs! These didn’t seem to represent a real threat to the birds – hence they weren’t too bothered by them, but the dogs seemed to enjoy running into the flock and putting them to flight ‘just for fun’!
The dogs were more interested in the Smooth Otter which can just be seen in the background. As for the otter’s interest – it was probably just naturally curious rather than having any serious intent at catching the birds. Still, all these things going on added to the interest of the afternoon!