By Àlex Ollé and Víctor Estrada-Devesa
Across most of the Iberian Peninsula, the local breeding Peregrine ssp is brookei. In the northern third of the peninsula, birds with phenotype very close to Central European birds are found. This is an integrade zone between peregrinus and brookei (Zuberogoitia et al., 2008).
From mid September to May, the local and sedentary brookei population in Iberia is reinforced with northern birds, originating from boreal and arctic areas in north and east Fennoscandia, that migrate through or winter in Iberia. Based on information from tagged birds and ringing recoveries, it seems that northern individuals wintering in Iberia originate mainly from northern Finland, an integrade zone between peregrine and calidus. Possibly Iberia also receives birds originating from arctic Russia, where pure calidus breed. In Catalonia –NE Iberian Peninsula, the wintering population is estimated at around 50 birds (Ollé, Estrada-Devesa & Gil, 2016).
In this post, we will try to add some interesting insights on the separation of brookei from northern birds (calidus or peregrinus/calidus integrades), mostly adults, based on our local experience in winter and on migration. We also present some interesting variation within brookei.
In adult birds, moult of flight feathers (mainly primaries) is the key feature to differentiate northern birds from local brookei. In Spain, brookei start laying eggs between late February and early March. Females start moulting earlier than males, in April-May. Males end their moult in October, a moult strategy completely different from northern birds. In September, when the first northern birds arrive back on their wintering grounds, they are in a less advanced moult stage, with only 2-4 central primaries moulted. Moult stage of Nordic birds may depend on egg-laying dates and on their breeding success, with early breeders of failed breeders arriving to Iberia with more advanced moult. Also northern birds show sexual differences in moult. In Catalonia we have noticed that females end their moult at the end of December, while latest males end their moult in April. On average, northern birds moult P10 (the last primary to be moulted) during the second half of February, though we found few individuals that were still growing P10 in April.
Moustachial stripe of northern birds is usually narrower, more pointed and more contrasting than brookei, especially at the base. Ear coverts are very white, almost up to eye level (photos 2, 3, 4, 8 and 7). Some birds can show wider and less contrasting moustachial stripe, but in no case blurred as in brookei (photo 1). The crown is normally pale grey, sometimes with a paler forehead (photos 4, 7 and 15). Conversely, brookei usually show a very wide-based moustachial stripe that links with less contrasting ear coverts, and a uniform dark crown (photos 6, 12, 13 and 16).
Body colours and patterns
Northern birds show a clear white upper breast, normally unmarked. The central breast and upper belly have irregular horizontal bars with little dark spots, that can reach down to the central belly area (photos 1, 2, 4, 13 and 7). Flanks show more regular stripes, but thinner. There is a clear sexual difference in this pattern: males have thinner and irregular markings, while females markings are wider and better pronounced. Base colour is a light and variable pale rosy tone (photos 2 and 13), especially in the central belly.
In brookei the base colour is salmon or cream, though in some individuals, mostly males, it is more restricted to the breast only (photos 6, 9 and 14). In brookei the upper breast usually has small dark spots, especially in females, that are followed by broader and regular horizontal bars, both in the central area and in the flanks (photo 6 and 9).
As mentioned above, males are on average paler than females. Northern birds are often paler blueish above, sometimes rather bright depending on light conditions.
Behaviour and hunting
Northern birds are often more human-tolerant than local brookei, sometimes even at very close distances (see attached video).
We found that northern birds often sit on the ground, much more than local brookei, that does not often land on the ground.
Northern birds are larger and heavier on avergae, and they prey on larger birds, including herons and ducks. Most often local brookei prey on pigeon-sized birds or smaller.
Young ‘Arctic Peregrines’
We believe that some birds wintering in Iberia are ‘Arctic Peregrines’ (calidus). They are huge! Young birds are very brown from above, and often heavily marked below.
Variation in adult brookei
Over the years we have noted some brookei that show features closer to northern birds (peregrinus / calidus). Without full study of all features including moult, they may be misidentified. More study is needed on the amount of variation in brookei.
We thank all the photographers for allowing us to use their photos.
Ollé. À., Estrada-Devesa, V. & Gil-Velasco, M. 2016. Els falcons d’origen nòrdic Falco peregrinus peregrinus i Falco peregrinus calidus: dues formes força descconegudes a Catalunya. Butlletí del CAC 1: 11-25.
Zuberogoitia, Í., Azkona, A., Zabala, J., Astorkia, L., Castillo, I., Iraeta, A., Martínez, J.A. & Martínez, J.E. 2008. Phenotypic variations of Peregrine Falcon in subspecies distribution border. In: Sielicki, J. & Mizera, T. (Eds.). Peregrine Falcon populations –status and perspectives in the 21st century-. Pp. 295-308. European Peregrine Falcon Working Group.