canberrabirds

Very silent friarbirds

To: "'COG'" <>
Subject: Very silent friarbirds
From: "Philip Veerman" <>
Date: Sat, 5 Dec 2009 15:07:50 +1100
Margaret,
 
About "How does a parent decide which of the three gaping mouths to put the insect in?  Do they know which is which in order that each gets adequate food?"

 

The general answer is as far as studies have shown the choice is not usually made by the parent. The adult bird puts food in the biggest and most available mouth or the chick that is the most demanding. In passerines incubation of eggs usually starts when the clutch is complete, so all the chicks hatch at about the same time, so in general there is not a big difference between them. So each has a sort of equal chance and when one has had enough it will stop begging and another one will have its share.

 

In things like raptors, owls, kookaburras, etc, incubation of eggs usually starts when the first egg is laid, so the chicks all hatch at different times and there may be direct competition between the chicks. The parents display no interest in ensuring that each gets adequate food. They feed the chick that is well enough to beg and it is not that odd for the younger chicks to be persecuted or eaten by the older ones, even while the parent watches. That is why survival rates in the biggest or oldest chicks is typically highest. If there is plenty of food available, then the bigger ones will have had enough often enough to not be the first to be fed and thus the others then get a go.

 
Philip
 
 
-----Original Message-----
From: Margaret Leggoe [
Sent: Saturday, 5 December 2009 10:22 AM
To:
Subject: [canberrabirds] Very silent friarbirds

I have been watching a noisy friarbirds nest on Farrer Ridge since 2 November.  On 24th, the behaviour of the parents changed, with the female leaving the nest more often, and being quite restless while sitting on the nest.  On one occasion I shot one of the birds bringing an insect to the nest, and guessed they chicks must have hatched.

 

Today was the first time the chicks were visible above the edge of the nest.  I saw two faecal sacs carried away in quick succession, but when I got home and had a closer look there were three chicks, and all looking quite robust.  I wondered how hard these birds would have to work to feed these three fast growing kids.  As I was leaving, one parent returned to the nest from at least 50 metres away, perhaps they have already cleaned out the ground in the immediate vicinity of their tree. 

 

How does a parent decide which of the three gaping mouths to put the insect in?  Do they know which is which in order that each gets adequate food?

 

At no stage since I began watching these birds have they uttered a single sound.  No doubt to protect the nest from detection.

 

Margaret Leggoe

<Prev in Thread] Current Thread [Next in Thread>
Admin

The University of NSW School of Computer and Engineering takes no responsibility for the contents of this archive. It is purely a compilation of material sent by many people to the Canberra Ornithologists Group mailing list. It has not been checked for accuracy nor its content verified in any way. If you wish to get material removed from the archive or have other queries about the list contact David McDonald, list manager, phone (02) 6231 8904 or email . If you can not contact David McDonald e-mail Andrew Taylor at this address: andrewt@cse.unsw.EDU.AU