It's not just birds that migrate but they would win gold medals at it. Whales do it, wildebeest do it, even educated painted ladies do it - but birds do it best in my humble opinion.
And in spring, now!, every time you go out into the countryside there may be another summer migrant returning to fill the air with its song. My list of summer migrants already seen is currently: swallow, sand martin, house martin, common tern, chiffchaff, willow warbler, blackcap, sedge warbler, grasshopper warbler and little ringed plover. Not bad, but others in Northants have seen wheatear, redstart, cuckoo, reed warbler, whitethroat, osprey, yellow wagtail, common sandpiper, hobby and even a swift. I'm itching to get out at the weekend and see what's about. And everything is so fresh and pretty at this time of year.
Now although each of those species is equally welcome back at my local patch of Stanwick Lakes, they have had very different journeys in order to get there. Take chiffchaff and willow warbler as two examples. Some chiffchaffs over-winter in the UK - more than used to - but those that do leave us go as far as southern Spain and North Africa to winter whereas willow warblers are trans-Saharan migrants, wintering in tropical and south Africa. And chiffchaffs are doing fine in the UK whereas willow warblers are declining in numbers.
Many other of our trans-Saharan migrants are declining in numbers but it's not just in the UK - such trends have been noticed in other European countries (eg Denmark) - and are there on a continent-wide scale. It's tempting to think that there's something going on 'over there' that is affecting 'our' migrants so that their numbers fall 'back here'.
That may not be the right way to look at it though. It still may be things happening here that are affecting those species - for example it looks as though willow warbler breeding success has declined recently in the UK. It's difficult to know without proper studies - and that is why, alongside our friends in the BTO, the RSPB is investigating these declines - 'here' and 'there'.
I can remember (I've said that a fair bit recently) when we were told that it was futile managing land for corncrakes here because all the problems were in Africa. It's a good job that we didn't take too much notice of this (but did keep it in mind as a possibility) otherwise the recovery of the corncrake would not have happened.
Just as any single migrant species might be having problems on its breeding range, wintering range, on its migration route or all or some of these, then that is just as true of all migrant species. I wouldn't be surprised if some of the problems are found to be 'here' and some 'there'. Fixing the problems 'there' might be quite challenging.
Nature conservation needs evidence on which to base its actions if they are to be successful. Sometimes you can strike lucky by guessing but there are plenty of examples of strongly-held views that were shown by research to be erroneous. And I guess that will apply to some of our currently strongly-held views too.
The work of the RSPB's science team has under-pinned many of the RSPB's success over the years - bitterns, corncrakes, stone curlews, cirl buntings, Hope Farm to name but a few. You don't save species just by studying them - you need to do something practical too - but it's noticeable, I think, that the RSPB has a stronger science team and greater science spend, than most other conservation NGOs (in absolute and relative terms). It can't be an accident that we have a long list of success stories.
Absolutely right Mark, the RSPB's strong science base is vital. Several other organisations could well "take a leaf out of the RSPB's book" in this respect. One get's nowhere by guessing or working off hunches and all that results from these are wrong decisions and actions , especially where nature is concerned which operates in complex and subtle ways. I think it was Carl Sagan, the famous astrophysicist. who said "you can't study nature by sitting in an arm chair" or words to the effect. As you say, the reasons for long distant migrant decline may be quite varied, with ways of reversing those declines being perhaps relatively easy for a few and difficult for others, but only proffessional study work such as that from the RSPB will tell us that.