There has been a lot of talk this week about whether or not our ospreys are already on the move: is spring migration already underway? There is certainly more than a hint of spring in the air here at Loch of the Lowes with many resident birds beginning courtship and territorial displays etc. Several sightings of Opsreys in the UK so far this spring have all turned out to be misidentified buzzards, but that doesn’t mean it isn’t possible.
What are our Ospreys doing right now? The vast majority of them will still be on their wintering grounds in West Africa, but the magnetic pull of northward migration must be starting to exert itself. Many birds respond to day length rather than temperature to time their migrations, which prevents them being caught out be unseasonal weather ‘blips’. But the urge to breed is strong and the birds must feel the instinctive need to move building.
The birds face a difficult dilemma: migrate early to ensure they arrive first on their habitual nest to stake their claim, and they risk worse weather on migration route and being caught out with cold and even freezing weather on arrival, making feeding themselves difficult. If they can lay eggs early, their chicks will be bigger and stronger by autumn, but they are at higher risk from loss during incubation to bad weather.
On the other hand, if they delay migrating to ensure better weather, they may arrive to find a usurper on their nest or even courting their partner! Leave it too late and their chicks will be at a disadvantage, being smaller and younger when facing their first difficult migration in the autumn.
How do the Ospreys ensure they arrive back at the nest in spring close together? We really don’t know. We know that Ospreys overwinter and travel separately, and that females usually leave Africa first, as they are keenest to get back to their nests, with the males often arriving in Scotland shortly after. Here at Loch of the Lowes, the female has almost always arrived first, with her various partners arriving between 1 day and 12 days after her. Observations elsewhere in Scotland suggest that if their partner hasn’t arrived back after two weeks of waiting, an Osprey may well assume its’ mate hasn’t made it and start allowing other eligible birds to court or mate them- so the moral of the story is “don’t be too late”!
The only way we can be sure if migration has really started is reports from our colleagues in Africa and on the Mediterranean routes, and by checking our satellite tagged UK birds to see if they are moving yet. Remember that last years chicks, (such as Einion, Leri and Dulas of the Dyfi Osprey Project in Wales), will not be migrating this year- they are still on their juvenile ‘gap year’.
Adults ospreys carrying trackers are the ones to watch: follow Rutland Osprey Project’s two adults males “AW” and “09” in Senegal and the Ivory coast currently ( 23rd Feb.), and Roy Dennis’s adults birds such as Beatrice ( Spain) and Morven ( Mauritania) and Red 8T ( Gambia) and 2yr old Rothiemurcus ( seen in Senegal In January).
All we can do is keep our fingers crossed for them and wish them well!