by Ken Wilson

April is perhaps the most dramatic transition month for birds and birders. Between the beginning of April to the end of the month, there is probably a fivefold or tenfold increase in songbird numbers. This abundance continues into May, declining quite a bit as the migrants continue onward, leaving a still substantial number of songbirds that will breed here. Most of these spring migrants are our ‘neotropical’ birds, mostly smallish songbirds that spend more of their lives in Central and South America than they do in our Pacific Northwest.

But why the late April arrival? Birds time their breeding cycle so that their food supply, often the juicy caterpillars that nestlings digest easily, is most plentiful when the parents have nestlings to feed. By arriving in late April and early May, the birds have available the intervening weeks for establishing territories, mating, nest-building, and incubation. These migrants arrive on schedule, plus or minus a week or so. They are cued more by daylength than by the unpredictable fluctuations of temperature from one day to the next. Go for a walk in late April and May when birdsong occupies nearly every habitat. It’s not essential to identify each song because the enjoyment itself is worth it. But an absolute must is to download an app called Merlin Bird ID. It enables your smart-phone to listen to singing birds and is astoundingly accurate in identifying each individual. Merlin will permanently change your relationship to birds. And not just in April. Enjoy.