Catalonia, Spain
Habitat = Birds
Catalonia, the area surrounding Barcelona, has officially the widest variety of habitat on the Iberian peninsular and, to be fair, probably Western Europe.
This of course means more bird species. Try this for a quick overview of the species available and the reasons why Catalonia should be high on anyone's 'to visit' list:
BIRDS -
http://www.catalanbirdtours.com/birds in catalonia.html
As well as a coastal stretch that includes several wetlands, the EBRO DELTA being the best of them, you have the PYRENEES to the North and STEPPES to the West.
SPRING SITES / ITINERARIES -
http://www.catalanbirdtours.com/spain birding migration.html
Top resident target species might include:
Dupont's Lark, Lammergeier, Eagle Owl, Little Bustard, both sandgrouse, Citril Finch, Black Wheatear, Iberian Grey Shrike, Iberian Woodpecker, etc, etc, etc
And migrants start with early Great Spotted Cuckoo and crakes, for instance, and just keep coming until you get to, in your date window, Roller, both nightjars, etc.
Accessibility
Being only a quarter the size of England, the vast majority of Catalonia's incredible bird life and top locations are accessible on day tours so you can base yourself in one location.
This means that, rather than being stuck at a birding spot in the rain because you've booked your accommodation, you can adapt daily, avoiding less than ideal weather forecasts, responding to local bird reports or simply change your mind on a whim.
The transport network of motorways is superb to take you to a massive range of reserves, about which there's a plethora of trip reports and other info on the internet.
You can fly cheaply to any one of three airport: Barcelona, Girona and Reus (plus another at Lleida actually).
Migration
Your timing in perfect of course for Spring migration but, unlike many other areas, Catalonia is on two major migration routes so you get double for your trouble.
There's plenty more to add so drop me a PM of you have any specific questions or want directing to any trip reports for a given period. I'll try to dig up a species list and PM it to you but if you want to send me a wish list, I'll recommend the best date window for you.
All the best and have a great trip wherever you end up.