Residing on Gibraltar, I’m, at 36oN, simply north of the Sahara Desert. I typically surprise what the fowl distribution could be like right here if there wasn’t a desert. I’d anticipate a gradient from these heat temperate latitudes right down to the tropics. It should as soon as have been like that. The desert creates an actual barrier, one which splits fowl distributions fairly severely.
However the distinction of trans-Saharan to pre-Saharan migrants shouldn’t be that clear-cut. Many species have wintering populations on either side of the desert: Blackcaps (Sylvia atricapilla) and Chiffchaffs (Phylloscopus collybita) amongst others. However there are but others which we take into account strict trans-Saharan migrants however which do retain wintering components north of the desert.
The Hoopoe (Upupa epops) is the prime instance for me. These birds attain us in massive numbers from tropical Africa within the early spring however others by no means depart. The numbers of Hoopoes wintering in Morocco and southern Iberia are substantial and I even see them frequently in winter within the central tablelands of Spain, round Toledo for instance. There’s clearly loads of meals for these birds to not go away for the winter. One other instance is the Wryneck (Jynx torquilla).
I’ve been in a position to doc the altering sample of birds remaining north of the desert over the previous many years. The perfect instance was supplied by White Storks (Ciconia ciconia). I can exit any day now and I’ll see White Storks. The change occurred within the late seventies and eighties as many birds remained and survived by dwelling from meals present in open refuse suggestions. That was not a climate-driven change however, as an alternative, by human actions.
A lot of different species are common in winter nevertheless it isn’t at all times clear if they’re wintering or returning as quickly as situations enhance. See my first put up, of 14th July. These birds might be wintering in small numbers and, if they can survive, could have the benefit of being near the breeding grounds and of not having needed to cross the desert. Amongst these species are Booted Eagle (Hieraaetus pennatus), Swallow (Hirundo rustica), Purple-rumped Swallow (Cecropis daurica) and Home Martin (Delichon urbicum).
Others are a bit extra excessive. There are occasional sightings of Quick-toed Snake Eagles (Circaetus gallicus) within the winter however, within the absence of energetic snakes, we’ve to surprise what number of of those survive in any respect. Maybe probably the most uncommon of all is the Pallid Swift (Apus pallidus). This fowl is a summer season customer however a couple of years in the past a big winter roost was reported in a constructing within the metropolis of Seville. If daytime temperatures had been excessive sufficient, there isn’t any motive why these birds couldn’t have survived within the decrease Guadalquivir Valley. It goes to indicate simply how versatile birds are and the way fast populations are in a position to answer adjustments in environmental situations. In edge areas like mine, I can not however assist feeling that I’m dwelling a pure experiment that’s occurring in entrance of my eyes.
