Wednesday, 25 July 2007






Homing & Hibernating

If you own a Budgie or Cockatiel you may have noticed that the bird usually sleeps on the same perch in the same place night after night. Well wandering about the forest at night I have discovered that some forest birds do the same thing.

This Sunbird was seen sleeping on the same centimetre of the same branch night after night for about 5 weeks in May-June. It’s disappearance was no doubt prompted by the fact that the branch was pruned by a falling adjacent branch. No trace of the bird was seen there after.

This Silvereye was observed sleeping on the same branch for more than 6 months in 2006 until its branch “disappeared” due to natural pruning. Each night the bird was observed in the same position on the branch. At times it was accompanied by another Silvereye but it was mostly on its own.

Ants and Raspy Crickets are known to have elaborate methods of finding their way back to their nests after a night’s foraging (see references below). They use the stars as guides by taking a mental “picture” of their surrounds before leaving and are able to find their way back to their nests and shelters after a night’s foray. In addition to the above, the Raspy Crickets (see the two photos) have individual marking pheromones that enable them to find their own shelters once they are in near vicinity where they began their journey. The cricket in the leaf enclosure is Xanthogryllacris punctipennis Walker. It, like all others in its family is active only at night. The other Raspy Cricket is an unknown species in an enclosure made from chewed pieces of bark. These crickets, like others of the Gryllacrididae, use silk, spun from the mouthparts, to secure and reinforce their shelters.

So it was with interest when this butterfly- the Varied Eggfly, Hypolimnas bolina-was seen night after night in May-June in the same shrub in nearly the same position. But discussion with Michael Braby suggested that the butterfly might be hibernation rather than returning home after a day’s foraging. A check of the site at a number of times over a period of days revealed that the butterfly was still at home. It was sedentary. Then in early July, it disappeared and has not returned.

References

Braby, M. F. 2004. The Complete Field Guide to Butterflies of Australia. 340 pages. CSIRO, Melbourne.

Hale, R., Rentz, D. C. F. 2001. The Gryllacrididae: An overview of the World fauna with emphasis on Australian examples. Pp. 95-111. In: The Biology of Wetas, King Crickets and their Allies. (L. Field, ed.). CABI 540 pp.

Morton, S. R., Rentz, D. C. F. 1983. Ecology and taxonomy of fossorial, granivorous gryllacridids (Orthoptera: Gryllacrididae) from arid Australia. Australian Journal of Zoology, 31: 557-579,

Lockwood, J. A., Rentz, D. C. F. 1996. Nest construction and recognition in a gryllacridid: the discovery of pheromonally mediated autorecognition in an insect. Australian Journal of Zoology, 44: 129-141.

1 comment:

Camera Trap Codger said...

Back in the 90s when the Bombay Natural History Society was doing studies in the Anamallai Hills of South India (Tamilnadu State), the young BNHS ornithologists discovered a rare and long forgotten species of nightjar roosting in the forest. It was an exciting discovery, and it was displayed to all visiting field biologists who were interested in taking a short hike to the site where you see it perched in slumber. It looked like a snag, and was a fine example of cryptic coloration. (Unfortunately I can't remember the name of the species.) But there it was everyday on the same perch.