An Imperial Beach Hidden Gem and Bird of the Week, the "Juvenile Least Tern"
Apr 12, 2017 09:06PM
By Paul Spear
Juvenile Least Tern (Sternula antillarum)
This week's "Bird of the Week" is the juvenile Least Tern (Sternula antillarum). The chicks of this endangered species hatched this year are now growing up and becoming juveniles.
Juvenile birds have dusky brown crowns and wings, with a dark shoulder and bar. They have gray upperparts by their first fall and their crowns become whiter, although they still have the dark shoulder and the bar. They are similar in coloring to the adults by summer, but still have a dark bill and legs. They sport dark eye patches and you will notice that their tails are not as forked as the adult birds.
Adult Least Terns are white with pale gray upperparts, white underparts and forked tails. They have rounded heads, without crests, black caps, and napes. These caps are less distinct in the winter. Black lines run through their eyes to the base of their bills. There are white triangular patches on their foreheads. Their bills are slender and pointed. In the summer their bills are yellow with black tips; in winter, their bills are black. Least Terns have short, yellowish legs which are darker and
less yellow in the winter. Their wings are pointed and mostly pale gray, with a dark area on the leading edge.
When you see juvenile least terns, you my have difficulty determining just what bird they are due to their different plumage coloring. There are now juveniles growing up in our own Tijuana Estuary. Be on the look out for them, and respect them by always keeping your dogs on leash, and giving them the space they need to grow into full adults.
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