I found an Alpine Swift Apus melba with a party of newly arrived Common Swifts Apus apus over Weston Park (SE185465) on the western outskirts of Otley, West Yorkshire. I watched the bird intermittently for 15 minutes before losing sight of it high over Otley Wetlands. This bird, the first for the Bradford Ornithological Group recording area, occurred during an influx of Alpine Swifts into Britain, and also coincided with an unprecedented arrival of Red-rumped Swallows Hirundo daurica in the country.

Hoping to see some summer migrants, I decided to go birding in the fields opposite my house in Otley on the morning of Saturday 26 April (the fields are known as Weston Park and from part of the Weston Hall Estate). I positioned myself on a small rise, known locally as Gallows Hill, which commands an excellent view towards the river Wharfe and Rombalds Moor beyond. I have found this to be an excellent spot from which to observe visible migration during spring and autumn.

As soon as I got in place on Gallows Hill I heard a party of swifts above me, among my first of the year. I glanced up before raising my binoculars, and immediately noticed a considerably larger swift with a substantially white belly with the Common Swifts. Realising this could only be an Alpine Swift, I hurriedly raised my binoculars, and enjoyed superb views of the bird as it joined the Common Swifts in a spectacular aerial display. Soon the bird was lost from sight to the north towards the hamlet of Weston, but within a few minutes it was back, and this time headed straight towards the river Wharfe with a group of swifts. Here it spent about ten minutes hawking insects at about 30-50 m above the ground, mixing with Swifts and Sand Martins. From my vantagepoint, this allowed me the opportunity to view the bird’s underparts and upperparts clearly, as it worked its way back and forth along the river valley.

The bird then drifted east towards Otley over the river and the main boating lake of Otley Gravel pits, gaining height all the time. It was lost to view with a party of Common Swifts high above the boating lake at about 9:00 am. I returned home to spread the news in the hope of other observers seeing the bird before it left the area, but unfortunately it was never seen again.

Description of the bird
When seen well, Alpine Swifts are very distinctive birds, and there are few identification pitfalls. The Otley bird was seen in good light, down to a distance of c.50 m, and in the company of Common Swifts and Sand Martins Riparia riparia for comparison. I was able to observe both its upperparts and underparts clearly, and it showed all the classic features of this spectacular swift.
Size and structure: Clearly considerably larger than Common Swift and twice as large as the attendant Sand Martins, with very long wings. The wing action was slower and deeper than the Common Swifts, but its progress very rapid. The bird was very powerful in its flight and was seen to outpace the Common Swifts on several occasions.

Upperparts: Uniform grey-brown above, paler brown than Common Swift, being much closer to Sand Martin in tone. I was able to look down on the bird from Gallows Hill as it hawked insects along the Wharfe valley.

Underparts: The most striking feature was the pure white belly, which contrasted with the brown underwings, vent and undertail at range. On its closest approach (c.50m) a white throat patch was visible, a feature which can often be hard to see in the field. This was well demarcated by a thin brown breast band, which separated the white throat patch from the white belly.

Behaviour: The bird spent almost all its time in the close company of a group of about 40 Common Swifts. Many of the these birds were taking part in agile aerial displays, chasing each other and calling excitedly, as if re-establishing pair bonds. The Alpine Swift seemed to want to join in, and chased a number of other swifts itself, as well as undertaking hair-raising dives and other manoeuvres in the sky. Later it hawked insects powerfully over the river Wharfe, loosely associating with Common Swifts and Sand Martins doing the same.

Confusion species: The combination of a large, powerful swift, with white belly and throat patch and pale brown upperparts is in Europe only found in Alpine Swift. Partly albinistic Common Swifts (of which I have seen several) are smaller, shorter winged and lack the paler brown upperparts of Alpine Swift. Although Sand Martin has a similar plumage to an Alpine Swift, it is clearly much smaller, has a completely different structure and has white extending from the belly on the vent.