Disturbance

Gretchen-the-biologist sent me a bulletin on herons a while ago. It's not for posting, because it was only a draft document ("Survey protocol for measuring reproductive productivity at Pacific GBH breeding colonies"), but I think it's okay for me to post this excerpt, because it is pertinent:

Colony response should be tested and recorded using Data Sheet #3 (Colony Disturbance Summary). The various responses by birds are as follows (record all responses that occur):

No response. Birds ignore the observer. They may stare and subsequently look elsewhere, as other activities occur in the colony.

Stare. Birds view is fixed on the observer. This is particularly noticed when birds peer over the nest at an observer in the colony.

Chortle or cluck. The first sign that birds are disturbed is a low nasal “cluck” (Vennesland 2000), or "chortle" (Moul 1990). This activity may be continuous or start and stop as movement of the researcher occurs.

Stand. Incubating birds rise off the nest, or move around in the nest.

Off nest. Birds leave the nest, but stay on a branch nearby.

Scream. After chortling, the next progression in vocal alarm is screaming. This is a very loud vocalization and usually occurs with, or immediately prior to, flushing. Researchers must never cause this disturbance as it shows extreme stress (such as during a successful predator attack).

Flush/Return. Birds fly away, typically as individuals, circle and return to the nest. Researchers must never cause this disturbance, as it can lead directly to colony abandonment.

Flush/Leave. Birds fly away as a group and do not return until observer leaves the colony. Researchers must never cause this disturbance, as it is likely to cause colony abandonment.

I'm not sure how researchers are to execute this test. When the leaves come down it'll be interesting to get the nest count.