Quiet Mice and Running Rocks

June 11 – June 24
John Vetter

A male Brewster's Booby and his chick. Photo: J. Vetter

Fig. 1. A male Brewster’s Booby and his chick. This subspecies of Brown Booby, distinguished by the male’s pale head and bill, is uncommon in the Hawaiian Islands. Photo: J. Vetter

Summer is in full force out here on Laysan, which unfortunately means a slowing of the Millerbird breeding season. Singing has dropped dramatically the last two weeks, and our last active nest fledged two more chicks, bringing the season’s total to 17 chicks fledged from 11 nests. Since most of the pairs are currently feeding fledglings, it may be another two to three weeks before we can officially put this season in the books, but at least a few pairs seem content with the young they have produced and have hung it up. A few of these have shown signs of post-breeding molt, with the birds losing their entire tails at once. This just reinforces the notion and appearance of quiet mice running through the vegetation.

One of the more important questions for us now is the dispersal and survival of the fledglings and juveniles. To that end, and for a clearer picture of the overall Millerbird population as we move forward, we have started banding these young birds as they leave their natal territories for parts unknown on the island. The Resight of the Week for this period goes to B/S, O/R, a female seen late last week after having eluded detection for over a month, despite feeding a young fledgling for most of this time.

Newly fledged Black-footed and Laysan Albatrosses have moved beyond the short air-time achieved from hopping into a strong wind to actually taking off from a running start, both from land and from the lake in the middle of the island, and flying around the island. With no down present and good control over their flight capabilities, many young Black-footed Albatrosses require a double-take to differentiate them from adults. In addition to these young birds fledging, many other young chicks have been hatching during the last two weeks. In particular, three species of tern now have chicks. Sooty Terns nest in vast colonies of hundreds of thousands of birds that ring the interior bunchgrass areas of the island, while Gray-backed Terns nest in smaller colonies of up to100 birds scattered throughout the low vegetation of the island. Both species have semi-precocial chicks that do their best to emulate a rock before darting out and running to another spot, where they then do their best to look like a different rock. The third species with new chicks are the bush- and tree-nesting Black Noddies, which build more traditional nests. These chicks (which would give any other chick on the island a run for the cutest) stay put in the well-constructed platform of leaves and branches.

No unusual migrants or vagrants showed up this period, which is to be expected in the summertime. We do, however, still have a couple of the brewsteri subspecies of Brown Booby nesting in the south of the island. One male has now been joined by a chick (Photo 1), while the other continues to incubate eggs.

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