Why should Black-tailed Godwits still winter in West-Africa if Southern Iberia is just as good? Expedition report Guinea Bissau, December 2015, University of Groningen & Global Flyway Network

From 7-19 December we visited Guinea Bissau on a Black-tailed Godwit ring-reading
expedition. We had planned our visit in December because we had hoped to get better
views of the (legs of the) birds when the rice had been harvested. Last year we were
here in November and it was sometimes problematic to see them well. Later in
December godwits are supposed to leave towards their staging areas in Iberia before
moving on to their breeding locations in NW-Europe.
Our itinerary mainly focussed on the huge rice fields along the Mansoa River. As
expected, the fields near Unche and Pache Iala turned out to be the primary location
for godwits (max. 1250 godwits) but we were surprised to see that nearly all other
sites we visited were almost without any birds. We could not find a clear clue for that
because fields were very comparable with harvest in full swing, dry fields close to the
villages and wet fields towards the mangroves and plenty of rice to forage on, either
on the plants, on the fields or on the dams. The birds we saw were all in excellent
condition and seemed ready for migration and had an average fat score (abdominal
profile) of 3,7 on a 1-5 scale (n=30).
As visiting random ricefields that looked good based on aerial pictures did not turn
out to be a very fruitful strategy, we switched to visiting also the more remote sites
where birds with satellite transmitters had very recently been seen like Ilha de Pecixe
and the area north of the Rio Cacheu. We found some small flocks of around 200
individuals at each of these sites but we never encountered large flocks like in Unche
or near Mansoa in 2014. This meant that getting resightings was troublesome and
after 10 days we finished our mission with 85 sightings of 48 individuals. In the
weeks before our departure the satellite tagged birds already showed quite some
movements in a northerly direction and we think we were simply too late to see big
numbers. As far as we can see, the reason for this departure can’t be adverse
conditions in Guinea Bissau where conditions were good and food was plenty.