Those who have been in recent years to New Guinea may have been lucky enough to see either Masked Bowerbird in the Arfaks of West Papua, or the closely related Flame Bowerbird in the southern lowlands of Papua New Guinea. The display behaviour of both species has been well-documented during recent BBC films (one of their hides we were even able to use on our tour a few years ago!), but myself and other bird tour leaders have regularly noted that there is an abnormally high incidence of males being seen destroying or otherwise abandoning their bowers.

Male bowerbirds are known to make their bowers at the start of the breeding season (usually over the course of days or weeks), and spend much of their time very close to their constructions to protect them from other males for the subsequent months. However at least these two species in the Sericulus genus can go for long periods of time without attending their bowers on any given day, perhaps to avoid predation due to their insanely vibrant colouration. It is also very common for the bowers to be "active" for a couple of days after a hide has been built, and then fall into disuse, this being especially true of Masked Bowerbird.

Last week, I was taken to a site in the Arfaks during our West Papua Vogelkop tour where the locals had found an active Masked Bowerbird bower several days previously. While no hide had been built yet, and there had been no disturbance to the bird, we arrived to find the bower already abandoned. The bower of presumably the same male was found later that day less than a hundred metres away, and we set up a very small hide overnight at a good distance from the construction. I was sitting very quietly in there at dawn, and observed a male come in and completely rip apart the entire structure in the span of about ten minutes before flying off. Was it the owner, so sensitive to disturbance that the mere sight of a nearby hide was enough to make him give up? I have seen Flame Bowerbirds do exactly the same thing, and this is an opinion often voiced by the local hide owners, but had always seemed a strange explanation to me.

An hour later, another male came in with an engorged tick on his face (proving he was a different individual, and this time seemingly the real owner). I watched in complete silence, and in slightly less than sixty minutes he had completely rebuilt the bower from scratch using the broken pile of twigs left lying on the ground. This single session in the hide was very enlightening, and indicated to me that perhaps it is normal for the males to regularly move the position of their bowers, especially since they can clearly rebuild much faster than I had imagined!

Later reading about the congeneric Regent Bowerbird of Australia (the only well-studied Sericulus bowerbird) surprisingly seemed to validate all these hypotheses. One comprehensive study (Lenz 1994) recorded adult males spending only 3.2% of daylight hours at their bower, with damage caused by intruders (both adult males and immature males) frequently leading to the abandonment of a bower by its owner. Lenz also observed rebuilds occuring an average of 64m away, usually finished within a matter of hours. What a contrast to most other species in the family!

All-in-all a very interesting field study of this spectacularly fascinating but still poorly-known New Guinea endemic, which certainly gives us some better information about how to improve our chances of a sighting on our future tours! He returned the following day and everyone else in the group saw him very nicely, even doing one short display to a female!

The owner of the construction, a male Masked Bowerbird (Sericulus aureus) which has almost finished rebuilding his destroyed bower. By Joshua Bergmark.