Spotted Flycatcher

Breeding distribution of Spotted Flycatcher
during the breeding-seasons of 2008 to 2011
(Click to enlarge)

Spotted Flycatcher has become a poster-bird for the cause of African migrants. Silver-haired birdwatchers will remember these as common birds of gardens, parks and orchards but a population decline of 89% between 1967 and 2010 has changed things massively.

At a first glance, the latest distribution of the species in Bird Atlas 2007–11 does not seem too bad. Spotted Flycatchers were recorded as confirmed, probable or possible breeders in 2208 10-km squares in Britain and 711 in the island of Ireland, these figures only being 232 and 180 fewer than in the 1968–72 atlas, respectively. However, using count information, it becomes easy to reconcile this apparently moderate spatial change with the dramatic fall in numbers revealed by combining Common Birds Census and Breeding Bird Survey data.

Breeding distribution of Spotted Flycatcher during the breeding-seasons of 2008 to 2011 (right). 
Change in breeding distribution of Spotted Flycatcher
(Click to enlarge)

The distribution changes are intriguing. If you click on the map alongside, to enlarge it, you’ll see that there are a few red, upwards-pointing triangles in Scotland and western Ireland, indicating further colonisation of new areas, and that most areas of Britain & Ireland are pink – with at least some breeding birds still present.  The overall impression is of the addition of a large number of black, downward-pointing triangles, representing losses from 10-km squares since 1988–91. At a time when the species is under pressure, perhaps we might expect to see gaps at the coastal fringes and in our biggest conurbations, especially Greater London the West Midlands and Glasgow, but why in a line from the Dee to the Humber? 

The change in breeding distribution (left): red upward-pointing triangles are new gains since 1988–91, open upward-pointing triangles are gains between the first two breeding atlases and solid salmon areas have been occupied since at least 1968–72.  Downward-pointing triangles indicate losses; black are recent losses and open triangles are losses between 1968–72 and 1988–91.

Breeding-season abundance of Spotted Flycatcher
(Click to enlarge)

The winter and breeding-season data collected by volunteers undertaking Timed Tetrad Visits have been used to produce maps of abundance for most of the species covered within the new book.  The map alongside illustrate the picture for Spotted Flycatchers, which are now very thinly distributed in Greater London and its environs. 

In fact, across mainland England and Wales, south of a line between Windermere and the North York Moors, the proportion of tetrad visits with Spotted Flycatcher has dropped from 31% to 9% in the last twenty years.  Focusing on northern England, the corridor of local losses from the Dee to the Humber now looks less odd – the line of black-triangles seems representative of processes taking place across a broader area and which have yet to be explained.  Across Ireland, there are still areas with relatively high densities of Spotted Flycatcher.

Using data from Timed Tetrad Visits, we can map the breeding-season abundance of Spotted Flycatcher (right), with darker reds indicating higher densities. 

Abundance change between breeding seasons
(Click to enlarge)

Much of the decline in numbers for the Spotted Flycatcher has occurred since 1988–91, and the abundance change map that has been produced for the new Bird Atlas 2007–11 illustrates the extent and magnitude of the losses. There is some good news in the extreme north of Scotland and southwest Ireland, though not to the same degree as shown by some other long-distance migrants, such as Willow Warbler and Garden Warbler, each previously featured as bird of the month (pick from list to the left). 

Across England, and particularly in the south and east, the changes have been massive.  In the New Atlas of Breeding Birds of Britain and Ireland there were plenty of red areas in the Home Counties and East Anglia, indicating high densities. These same areas show up strongly in the abundance change map that will be published this time around, in some of the darkest brown tones. Perhaps the species’ range is on the verge of collapsing?  As we lose the last pair in each square, perhaps from a churchyard or special wood, then the full extent of the loss will hit home.

Change in abundance (right) has been calculated using the timed counts from the breeding seasons of 1988–91 and 2008–11. Deeper pinks show gains and darker browns show losses. Gaps indicate areas where change was minimal, or the species does not occur in sufficient numbers to calculate a change.

by Graham Appleton

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