I have been
fortunate again this breeding season to assist Deb Sullivan, BirdLife Australia
Project Officer Gippsland Lakes, with monitoring Fairy and Little Terns and
Pelican breeding colonies on the Gippsland Lakes.
For more
information and background on the Eastern Crescent Island Pelican breeding
colony see an earlier post here: http://avithera.blogspot.com/2017/02/pelican-rookery-crescent-island.html
The 2018/19 Eastern Crescent Island Pelican rookery crèche on 5/12/18 – there are about 50 young birds in the crèche. |
There has been a separate Pelican breeding colony at the Western end of Crescent Island which first bred there in 2016/17 and again this season – they missed breeding there in 2017/18. This colony started much earlier than the Eastern colony.
Recently we
observed an adult Pelican feeding its chick at the Eastern colony. The event
took some time to unfold. At first we could see a possible feeding about to
take place when an adult bird moved about amongst some young birds on the edge
of the crèche with its wings held partially out which seemed to be a signal
that a feed was on offer. However, it was not clear initially which chick
belonged to the adult as several chicks showed interest.
After
several chicks attempted to gain a feed, one bird emerged as the most likely
contender to be fed. However much begging and manoeuvring was required by the
chick before the feed was finally given. (1)
After the initial melee, the begging chick seen here looked to belong to the adult bird. |
The chick persisted in begging. |
The young bird to the left was still excited but did not attempt to approach the adult bird. |
It is hard to interpret this behaviour, as it is with much animal behaviour. The young bird clearly wants to be fed so its begging behaviour is clear. However why the adult is so slow to give in to the begging and provide the chick with the food it so clearly wants is hard to understand. (3) Why does the parent withhold the food for so long and make the chick expend so much energy begging for a feed? Perhaps the parent is deliberately making the chick work for the feed, but is this for the exercise or survival value or is it to make the chick demonstrate it is really hungry and needs the food? Can greedy chicks consume more food than is good for them?
At this point the adult and chick have turned away from one another and I thought we may not see a feed given. |
The chick persisted and returned to touch the parents bill. |
Still the manoeuvring continues. |
Another bill-open moment. |
This is looking more like a feed is about to take place. |
The time taken for the begging ritual was about 4 minutes and 30 seconds.
Finally the chick has its head inside the adult’s bill and its bill down the adult’s neck/throat. The adult is regurgitating food. |
The feeding went on and on. |
The total time for the feed was nearly 3 minutes. (4)
Chicks can become seriously oxygen deprived during feeding and can take some time to recover following feeding including exhibiting strange drunken like behaviour and aggression towards surrounding Pelicans – more information about this behaviour including photos can be found here: http://avithera.blogspot.com/2018/01/australian-pelican-juveniles-strange.html
The total
time from when we noticed a feed was on offer to the finish of the feed took
about seven and half minutes - I am not sure if this is typical for chicks of
this age – obviously very small chicks are fed smaller quantities of food more
often and no doubt the very young chicks do not have to expend so much energy
getting their parent to give over the food.
A word
about bird ethics. This Pelican breeding colony is on a narrow sand island
beside a relatively busy waterway with many boats passing close by. The birds
have adjusted to this level of disturbance. Our observations were made from a
boat positioned some distance off-shore and the photos were taken with a telephoto
lens (600mm focal length) and cropped later during processing of the images. By
this means there was no disturbance to the colony.
In the next
few weeks many of the young in the photos will be fitted with a metal leg band
and a numbered brightly coloured plastic band and blood and DNA samples will be
taken as part of the monitoring work under contract to DELWP.( 5)
NOTES:
Comments added by Deb Sullivan
(1) Adult
birds appeared to deliberately remain distant from the main crèche which left
the chick to seek the parent.
(2) This
behaviour could also be sibling rivalry if the adult successfully managed to
raise more than one chick to this stage.
(3) The
length of time taken to actually allow the chick to feed could also be parental
preparation. It must take an enormous
amount of physical effort on the parent’s behalf to accommodate the chicks
physical shape. I also suspect that the crop would need rotation to allow the
chick to feed as well.
Some adults do this much
faster and require little begging time from the chick to encourage
regurgitation.
(4) The
average time recorded over many feeds last year took approx. 2min:45sec. The length of time this female took to feed
this young one did appear to be much longer than I have witnessed before.
(5) This
is a BirdLife project funded under the Gippsland Lakes Consultative Committee.
Licensing is through the Australian Animal Ethics and Departmental licensing
(it is multi agency permits)
No comments:
Post a Comment