Thursday, 3 April 2014

Nightime update
With large numbers of warblers still on the island by yesterday evening, it was perhaps no surprise that a sizeable lighthouse attraction was underfoot. The steady movement of migrants through the island, coupled with the settling of low cloud and drizzle in the early evening, meant that it was a rather busy night!

At about 2240 last night, the small shapes of migrants illuminated by the lighthouses' beams could be seen over the South End. By 2320, Obs staff had converged on the South End, and within half an hour, the flood lights were ready for action- pointed downward to illuminate the ground, their purpose to bring the dazzled birds away from the lighthouse. These birds can then be caught, thus saving them from eventual exhaustion from repeated impacts against the lighthouse.

At closer quarters, it could be seen that there were between 300 and 500 birds circling the top of the lighthouse: this total comprised a mix of phylloscopus warblers, Blackcaps, Wheatears, Manx Shearwaters, and a single 'Eared' Owl, which darted through. During the next few hours, a trickle of birds were enticed down from the mayhem above, and were captured by means of hand nets. In total, 40 birds were caught, which were then ringed in the early hours, before release. Amongst these were some rather smart birds...

A total of five Wheatears were trapped, this one being the only obvious Greenland-race bird. With a wing length of 110mm, a weight of 29.5 grams, and a tarsus length of 28.6 mm, the biometrics of this adult male leucorhoa gave the impression of a small thrush in the hand, rather than a Wheatear!

Some video footage from the attraction (the small dots are the birds, although you will have to try and picture there being about 100 times the number seen in the video!):
(c) Steve Stansfield

Daytime update
It was clear that, by morning, a large number of migrants had been forced to make landfall on the island, with Blackcaps and Willow Warblers bursting out of every crevice and gorse bush on the island. A small amount of light rain throughout the morning kept many birds on the island, although it was very much apparent that most migrants were moving through quite rapidly.

The first Grasshopper Warbler of the year was heard reeling away in the New Plantation, representing the second earliest record on Bardsey; the earliest was seen on the 1st of April, 1999. Two Firecrests remained mobile around the Nant area, whilst hirundine passage over the coast comprised three Swallows, 22 Sand Martins and two House Martins. Warbler numbers reached their highest figures so far this year, with minimum totals of: 150 Blackcaps, 204 Willow Warblers, 45 Chiffchaffs and 15 Goldcrests. A grand total of 60 Wheatears was also the year's highest total so far.

Willow Warbler
This rather stunning Oak Beauty was attracted to the Lighthouse beams last night. This species has not been recorded on Bardsey before. The larvae feed on a range of deciduous trees, and so this moth is likely to be a vagrant 
The male Oak Beauty sported a fantastic pair of bipectinate antenna. Antenna are extremely sensitive, generally used to detect female pheromones from a distance. Members of the lepidoptera family Saturniidae (for example, the Emperor Moth) and many other families can detect female pheromones from distances of up to 2km.

No comments:

Post a Comment