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STEVENS - PINK-BACKED PELICAN



especially unpaired males, can disturb the breeding activities of pairs by

seizing their nests and breaking their eggs.


This may have been the cause of problems at Longleat, where the ratio

of males to females at the time of the study was 10:5. Many of the birds

in the colony are hand-reared birds, but without further research it is not

possible to say whether this has had a detrimental effect on their ability to

successfully rear their own young. An advantage of hand-reared birds is that

they are calm and steady around the keepers, which makes nest inspections

relatively stress free. Another problem that was encountered was the death

of a chick at the point of pipping, thought to be due to a problem with the

humidity in the nest (Wexler, 1997). Of the eggs that were left in the nests

to be incubated and the chicks reared naturally in 1999, only 12 of the eggs

hatched and none of the chicks survived past 16 days old. Neglect by the

parents, a retained yolk, leading to a yolk sac infection, and ejection from

the nest (it is not known if this was by the parents or by other members of

the colony) are thought to have led to premature deaths.


Tierpark Berlin has a mixed colony of Pink-backed and Great White

Pelicans P. onocrotalus. The presence of the Great White Pelicans has had

a detrimental effect on the breeding success of the Pink-backed, as they kill

Pink-backed chicks and disturb the adults whilst they are breeding (Kaiser,

2006). These are just some of the problems which make it necessary to

hand-rear this species, in order to achieve breeding success. However, at

Odense Zoo and Vogelpark Avifauna, they prefer to leave the parents to rear

their own young, in order to avoid imprinted birds.


Incubation


The nests are checked for eggs once or twice a day, and any freshly laid

eggs are removed for artificial incubation. All eggs are weighed before being

placed in the incubator and are weighed throughout the incubation period.

They are incubated at a temperature of 37.5°C (99.5°F) and 60% humidity

and should achieve a 15% weight loss during the 30-34 day incubation period.

This is plotted on a graph and is carefully monitored. If the weight goes

significantly over either side of the 15% weight loss line, the humidity must

be adjusted accordingly. If an egg is losing too much weight, the humidity

needs to be increased. Similarly, if an egg is not losing enough weight, the

humidity needs to be reduced to create a drier atmosphere in the incubator

(Harvey, 1990). It can be a good idea to have two incubators set at different

levels of humidity, especially if incubating more than one egg, as individual

eggs may have different requirements.



