Monday, July 29, 2013

Arctic Tern Study

The BTO have been putting together a series of identification videos and now and again I spend some time going through these to remind myself of key ID points on some potentially confusing species. They really are most useful and to date there are 27 videos covering over 60 species. This morning I was taking another look at the one titled: 'Taking a Look at Terns 1: Arctic and Common Terns.' These two species can be a little tricky if you are not sure what to look for. This prompted me to post a few of my Arctic Tern shots. When you have had a good look at these I recommend checking the BTO video by clicking on the following link:
These pictures were taken at the colony on Inner Farne in the Farne Islands, Northumberland. Whilst we were there we had good views of two breeding Roseate Terns but we had left by the time the Bridled Tern turned up!
The main ID features of Arctic Tern are: a blood-red bill without a black tip, which can be seen best on the third photograph. (The bill of a Common Tern tends to have a distinctive black tip and the bill of a Roseate appears to be all dark with a red base.) The throat, breast and belly tend to be washed grey and this forms quite a clear contrast with the white of the cheeks. This feature can be seen on the photos of the bird in flight as well as the perched birds. (This contrast is less obvious on Common Terns and not really present on Roseates.) Arctic Terns have very long tail streamers which extend beyond the wing tips when the bird is perched as you can see in the second photo. (The tails of Common Terns do not extend as far as the primary tips.)

Arctic Tern Sterna paradisaea   Adult
Arctic Tern Sterna paradisaea   Adult showing length of tail and contrast between the grey under-parts and the white cheek.
Arctic Tern Sterna paradisaea   Adult showing blood red bill.

The flight shots show that the flight feathers are translucent and almost pure white when viewed from below and the outer primaries have a neat black trailing edge. Common Terns would show a much broader diffuse black trailing edge to the primaries.
Arctic Tern Sterna paradisaea   Adult. Note the distinctive contrast of the cheek

Arctic Tern Sterna paradisaea   Adult showing the neat black trailing edge to the primaries.

Arctic Tern Sterna paradisaea   Adult - note the white, translucent flight feathers.

Arctic Tern Sterna paradisaea   Adult

Other ID features of Arctic Tern, useful for separating it from Common Tern, are its slightly smaller size, shorter legs, narrower wings, uniform pale grey upper-wings which lack the dark wedge found on Common Terns and its more bouncy flight. None of these features can be seen on these pictures and you really should see the birds side by side to benefit from some of these points so go and take a look at the BTO videos.

Monday, July 8, 2013

Nightjar Chicks

Last Saturday I drove down to the BTO headquarters in Thetford to attend the OSME general meeting, more of which later. After the event had closed at around 5.00pm I took some time to visit a part of Thetford Forest to take a couple of photos of Nightjar chicks. A friend was looking for Adders last week when he flushed a female Nightjar and in doing so he located the nest which contained two recently hatched chicks. So armed with a 400mm lens, so that I could shoot from a reasonable distance as well as a 70mm lens to get shots that shows the nest site, we strode purposefully into the forest!

Typical Nightjar habitat in Thetford Forest
It was particularly hot and as it was not yet really evening there was not much in the way of bird activity. A couple of Wood Pigeons flew over and a Yellowhammer was singing from a nearby pine as we approached the site. The female took flight as we neared the nest and pitched in to an oak about thirty metres away. She was obviously keeping an eye on us and we suspected that the male was probably resting up pretty close by too.
Nightjar chick - close-up
Not wanting to get too close or to be too long at the site I took pictures using the 400mm lens. The chicks had their eyes open and were both looking healthy and well. These birds prefer open areas in which to nest, especially lowland heath, clear felled areas in forests and young conifer plantations

Spot the chicks!
The nest (which really is a misnomer as there isn't one) is a slight scrape at most and more often just a suitable patch of ground as was this one - as can be seen in the photos.

Nightjar's nest!

Nightjar chicks at approximately one week old.

 The young rely on their cryptic camouflage and by remaining still to avoid being detected. I was told that when they are handled by licenced ringers they remain perfectly still and calm and do not need to be placed in bags as they are so sure of their invisibility they don't really think they are being handled at all...because nobody can really see them!

Nightjar chicks