What was done
The authors analyzed a huge database of about 44,000 records for five trans-Saharan bird species (Ciconia ciconia or white stork, Cuculus canorus or cuckoo, Apus apus or swift, Hirundo rustica or barn swallow, and Luscinia megarhynchos or nightingale) that they assembled from observations made at more than 1300 sites throughout Spain during the period 1944-2004 in a study of the birds' migratory behavior, which phenomenon had previously been proposed by the country's Instituto Nacional de Meteorologia as "a potential bioindicator of the timing of seasons," the current study of which the two Spanish researchers describe as "the most complete and thorough analysis available for the Mediterranean region."

What was learned
Gordo and Sanz report that "spring arrival dates have tended to advance since the mid-1970s," and that "individuals arrived earlier in warmer years," noting that "the earlier arrivals related to higher temperatures should be due to the advancement of the spring course in the Iberian Peninsula and consequently the presence of ecological suitable conditions for an early colonization of first breeders." Of most interest to us, in this regard, is their finding that "current arrival dates are similar or even seem to be a bit later [our italics] to those occurring at the beginning of the study period."

What it means
Although most climate alarmists discuss the subject of this study within the context of what they describe as a late-20th-century global warming that was unprecedented over the last two millennia or more, Gordo and Sanz say "the advance in arrival date recorded over the last few decades should be better interpreted as a trend towards re-establishing the timing of migration after an anomalous period of delayed arrivals during the 1970s-1980s," which suggests that temperatures throughout the Mediterranean region were likely warmer in the mid-1940s than they were throughout the 1990s and during the first years of the 21st century, a situation that has been observed to have prevailed throughout many parts of the world.