2003 Warbler arrivals

Warbler arrivals, March-April 8th 2003
Of the three warbler species that have currently arrived, Chiffchaff and Willow Warbler have both equalled their earliest arrival dates for the area, whilst Blackcap equalled their latest ever arrival date. Such variation in dates is surprising, but similar to that achieved by other Summer migrants of which at the time of writing (April 9th) Common Tern and Ring Ouzel were very early, yet an expected and normally early migrant such as Sand Martin has yet to occur.

Spring arrivals (up to and including) April 8th 2003 Equivalant Spring arrival table for April 8th 2002

Arrivals/males currently holding territory - April 8th 2003

	Arrivals	In territory
Chiffchaff	32	14
Willow Warbler	3	0
Blackcap	2	1

The differences found, when comparing the arrival tables from 2003 and 2002 (produced above) even at this early stage of the arrival period are noticeable. Chiffchaffs have generally arrived earlier this year and in good numbers, but the basic arrival pattern however remains quite similar to most previous years. The biggest difference comes when looking at how Blackcaps have arrived.

What has happened is that Blackcaps have in fact equalled their latest ever date, of April 7th 2000. This is perhaps surprising, as the fine conditions experienced throughout most of March, were thought extremely likely to have allowed a new earliest arrival date. The number of male Blackcaps holding territory at sites within the area, are currently well below previous counts for April 8th in previous years.


Warbler arrivals, April 8-16th 2003
An interesting comparison with the same date in 2002. The fine and settled weather has allowed a steady trickle of arrivals into the area, but for some reason (possibly strong easterly winds along the southern UK coast) migrant Blackcaps were held up. A low pressure system south of the UK produced gale force southerly winds and it's on these that Whitethroats appear to have caught up and produced a very early arrival date of April 15th. With four arriving this morning (16th) it seems that warbler migration is now about a week ahead of normal. Arrivals on these latter dates are some of the most significant arrivals since records began here in 1998. The weather during much of March (up to and including the latest date below) has generally been completely dominated by much fine weather as high-pressure systems dominated the UK's weather. Potentially this should have allowed the opportunity for migrants to arrive early and possibly be able to travel much further during a night-time flight than in a typical (wet) Spring.

Spring arrivals (up to and including) April 16th 2003 Equivalant Spring arrival table for April 16th 2002

Warbler arrivals, April 16-23rd 2003
The second good arrival into the area followed on April 22nd, coming on the back of a return to south-westerly winds. The intervening period since the last update (16th) saw Sedge Warbler provide a new earliest arrival date, whilst Lesser Whitethroats have generally began arriving on time. Strong easterly winds across the southern UK are most likely responsible for the lack of any arrivals just after mid-April.

Spring arrivals (up to and including) April 23rd 2003 Equivalant Spring arrival table for April 23rd 2002

Arrivals/males currently holding territory - April 23rd 2003

	Arrivals	In territory
Blackcap	37	22
Chiffchaff	43	20
Willow Warbler	29	14
Whitethroat	27	12
Lesser Whitethroat	2	1
Sedge Warbler	2	0

The above table shows the current male populations within the area. Many of the first wave of male Whitethroats (the majority of which arrived around April 16th) moved on once the strong easterly winds had dropped and at the return of favourable migratory conditions. During their stay, most rarely ventured into full open song flight, more commonly producing the characteristic and quieter sub-song and remaining hidden for long periods. Both Willow Warbler and Blackcap continued to arrive and establish territories throughout the period and the first Lesser Whitethroat and Sedge Warbler appeared. Produced below is the final arrival table for the entire Spring migration period in 2002. Arrivals were severely hampered by two areas of low-pressure during the course of the Spring period, most especially during the second week of April. The efffect of which caused a complete halt in migration by most species at the time.