Interesting Tern Behavior Caught on Tape
When we see a tern waiting in a tree with a fish we typically assume that it's waiting for a chick to return for its daily food allowance. It turns out that a tern waiting with a fish could also be waiting for the other kind of chick! Courtship feeding - when a male feeds a fish to a female mate, or prospective mate - is something that other tern species commonly do. White terns on Oahu either do it rarely, or they tend to do it out of sight.
While observing terns at Holy Nativity School in Aina Haina recently I saw some strange behavior involving two adult terns and a fish. It took place close enough and went on long enough that I was able to video much of it on my iPhone.
The action starts with an adult (male) landing in a tree with a fish. Another adult (female) immediately comes over and lands next to him. They then make a brief circular flight from the tree and then return together. This is where the video starts. The female seems to know how this is supposed to work and, shall we say, “proactively accepts” the fish. The male seems less certain about how the game is played and is slow to let the fish go. The female then begins to preen the male, which he appears to enjoy and is sufficiently distracted that she is able to slip the fish from his grip. What’s really strange is that she doesn’t immediately swallow the fish. Instead, she seems to tease him with it. The fish play goes on a bit more after the video stops and eventually the fish falls to the ground. The pair then engages in an extended session of allopreening.
I shared the video with a couple of seabird experts. The consensus is that this is probably an inexperienced male awkwardly trying to entice a prospective mate. Or, it could be that this young male has shown up with a good looking fish and an aggressive female is “coming on to him”, trying to separate him from his fish. Either way it’s an example of tern behavior that we should be on the look out for. As Eric VanderWerf (Pacific Rim Conservation) pointed out, if you see a white tern flying around with a fish in his mouth you can be certain that he’s not just carrying it around. What’s not so certain is which kind of “chick” he intends to give it to!
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