Marsh harriers are highly variable between ages, sexes and individuals, and (adult males in between) can be confusing at the best of times. Add in the 500m range, often poor visibility and fast-growing scrub, and a close look at individuals in Corse, and so deciding how many birds are around can be difficult. Thanks to some post-match analysis of some remaining photos by Caroline Pickett and Alan Merrett, we now know we had at least 4, maybe 5 individual marsh harriers in Corse throughout September and October. though no more than two are seen on a given day.
Caroline and I had a brief insight into the type of adult woman in our WEBS count last September (21.09). We later learned that Alan Merrett saw the two together on 19.09. His photos show that these are both likely 1CY birds, one of them by its broad body almost certainly a female, the other probably a female, but neither were not clearly adult birds after two days. (Juvs in September – where did they come from? Our tagged bird from Norfolk in 2020 came out in November). Caroline and I saw an adult female in our next WEBS count on 19.10: useful, it comes from a primary. A few days later, Caroline and Alan saw two birds together, both adult females. Finally, yesterday, Caroline photographed this female, clearly our bird from 19.10, according to her missing primary.
So: two 1CY birds and an adult female in September, two adult females in October – one of which may or may not be our September adult. Great job Caroline and Alan.
1. Alan’s birds from 19.09.2024 are both likely 1CY types, the lower one is a female by its wide body:
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photos Alan Merrett
2. Caroline’s and my bird from 21.09.2024, under usual conditions – 4-500m, poor visibility: buzzard on the fence – cream-yellow reaching the sides of the neck, probably a 3CY+ ♀ moulting on the left primary:
3. Caroline’s photos of 2 birds, both adult females, on 21.10.2024 – one of which (maybe) we found on WEBS two days ago. Bottom c/u is above, additional bird in photo of two:
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photos Caroline Pickett
4. Finally, Caroline’s ad pic. girl type taken yesterday. From the missing left primary, this looks like the bird we saw on 21.09 (above):
photo Caroline Pickett
Great job Caroline and Alan. Thoughts and comments on feathers are welcome, nothing says this post is definitive! (Forsman devotes a page to separating female marsh harriers, black kites and dark phase booted eagles out of context/on the trail, a problem we don’t have in Corse!)
