Friday, 7 December 2018

Pelican feeding chick

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:

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 adult is standing tall with wings held out and bill high. The chick must stand tall to use its bill to try and get the adult to open its bill for a feed. I suspect the young one is holding its wings out for balance.
Several excited young that had attempted to beg a feed continued to jostle among themselves after it was clear which chick belonged to the adult. This pair have locked bills as they work off their excitement. (2).
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.

The other young in the area moved about at times surrounding the pair. At this point the adult for the first time has opened its bill and the young one is attempting to insert its bill. However the adult’s head and bill are far too high for a feed at this stage. 
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:

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)

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