Migration blog (21st May – mid-June)

The past week saw a continuation of previous weeks' weather with low pressure systems coming in off the Atlantic – more akin to what would be expected in late autumn. The cold temperatures and unfavourable wind directions continued to keep migration at a trickle with no big arrivals of migrant species noted from the usual hotspots.

The BirdTrack reporting rates for both House Martin and Swallow took a dip last week with the reporting rate for Swift also below average, possibly due to some birds having not arrived but also due to continental breeding birds not passing through Britain and Ireland as a result of the lack in south or south easterly winds. Wood Sandpipers were also thin on the ground with a drop in the number of birds being reported; it seems the peak arrival was last week, slightly early this year, with the majority of birds passing through in that week. Lesser Whitethroat reports were up on where we would expect for the time of year but the reporting rate this year looks to be about a week behind where it should be due to the cold spring. All that said, birds are still arriving, just not on the scale that we are used to with no real big arrivals of birds at bird observatories or other migrantion hotspots.

Species such as Turtle Dove and Spotted Flycatchers which are typically late arrivals were still reported but later than normal and at lower levels. There is still time to take part in The National Turtle Dove Survey – a partnership project coordinated by the Rare Breeding Birds Panel (RBBP) and the RSPB, with support from BTO and Natural England.

We will have to wait until the results of some of the other BTO surveys, such as BBS, are published before we know the full extent of the impact this cold spring has had on summer migrants. There could also be further impacts if we have a colder or wetter than normal summer.

Some scarcer species did arrive across Britain and Ireland with a White-throated Sparrow in Shetland the rarest, but other rare species included Franklin's Gull in West Yorkshire (also seen in Norway and Belgium earlier in the year), Collared Pratincole in Kent, Caspian Tern in Norfolk, and a Squacco Heron in Ceredigion.

Species focus — Honey-buzzard

Its very name conjures up an image of a bird that would be associated with warm climes and so it is. Honey-buzzards are long-distance migrants, spending the winter months in tropical and South Africa and breeding during the summer months as far north as Scandinavia. The main area for British breeding birds can be found in its southern coastal counties from Dorset to Kent but it can also be found breeding in Wales, Norfolk, North Yorkshire and in Scotland.

Spring migration across the Strait of Gibraltar occur from mid-April through to early June, peaking in mid-late May and the first arrivals in the UK can be recorded from as early as mid-April, but the typical arrival period is mid-late May. The few ringing recoveries there are suggest that British breeding Honey-buzzards spend the winter months in tropical West Africa, with outward bound migration from Britain recorded from early September through to late October.

The current British breeding population estimate is 51 pairs. Honey-buzzards spend a lot of time on the ground in search of the nests of bees and wasps, hunting for both comb and grubs within any nests found and as such can be very secretive during the breeding season.

The European breeding population is many times greater that the British one and in certain weather conditions a hint of this can be seen when large numbers get drifted into Britain on both the northward migration in the spring – a period of south easterly airflow can result in this – and in the autumn during periods of easterly winds. So far this spring, the weather hasn’t been the best for drifting birds from the continent.

From early June the pace of migration slows as the majority of summer migrants will be busy breeding.  

Looking ahead

The low pressure system that has just crossed Britain and Ireland bringing with it gale force south westerly winds is set to continue, producing strong winds along the south coast during the weekend which could result in birds being pushed into the Channel or up the Severn Estuary. The most likely species include Kittiwake, Little Gull and skuas of all four species. Long-tailed Skuas especially will be heading up the west coast of Britain, through the Irish sea, and up past the Outer Hebrides and can pass sites such as Aird an Runair at Balranald on North Uist in good numbers, with 2015 being an exceptional year and one many birdwatchers dream of seeing.

Red-necked Phalaropes will also be migrating at this time of year. These can turn up at inland waters after strong onshore winds. Their spinning feeding behaviour is great to watch and unlike many other species the females are brighter than the males and once they have laid a clutch of eggs they leave the male to brood and raise the young. Nightjar is also a late arriving migrant and these will continue to arrive over the next couple of weeks – warm calm evenings are the best conditions to look for them on heathlands but it is also possible to find them on migration where they can be found almost anywhere, including perched atop garden fences.

As we progress through the coming week the winds turn more northerly and colder temperatures are set to return and but drier conditions for many. As with past weeks this is only likely to compound what has already been a poor spring for migration as birds struggle to push northwards.

Early to mid-June sees migration slow as most of the summer migrants will have arrived and be getting on with breeding. Depending on the weather there are still a few species that could arrive over the next couple of weeks – for example both Quail and Marsh Warbler are scarce breeding birds across Britain and Ireland and are typically late arrivals. Quail can do a staggered migration and even breed in one location before moving northwards and breeding again in another country. This typically elusive species is best listened for around arable fields and meadows, their “wet-my-lips” repeated song is often the only way of knowing a bird is present. Marsh Warblers are equally as skulking and their song, which is full of mimicry, is the best way of locating a bird and they prefer scrubby habitat with nettle beds or similar vegetation to breed in. Always think carefully whenever you find a scarce breeding species about whether to put news out or not, always put the bird first and record any breeding evidence via BirdTrack to help both county recorders and the Rare Breeding Birds Panel monitor the populations of these rare breeders.