Date: July 28, 2014
Source: Behavioral Ecology
A four year study indicates that the
parrotbill exhibits a cognitive mechanism described as online self-referencing
in order to recognize its own eggs, according to a study published July 28,
2014 in the journal Behavioral Ecology
by Dr. Canchao Yang and his colleagues.
Behaviors involved in egg recognition
have been recorded in parrotbill nests in the Kuankuoshui National Nature
Reserve in Guizhou in the southwestern region of China from August 2009 to
August 2013, but before then ecologists did not have such a strong
understanding of the cognitive mechanisms used in parasitic egg recognition by
this brood parasite host laying polymorphic colored eggs. The goal
of this study was to further the understanding of the mechanisms that the
parrotbill uses to distinguish its own eggs from parasitic eggs laid by the
eleven species of cuckoos in the area.
The authors of this study assigned
parrotbill nests to 12 treatment groups by manipulating the combinations of
eggs (made up of their own eggs or parasitic eggs) in the nest that each set of
parents was given, and collecting data 1-2 days after clutch completion and
monitoring the nest for the following six days. Responses were classified as
parasitic eggs rejected, own eggs rejected, or all eggs accepted.
Researchers found that there was no significant
difference in treatment response between hosts that lay blue eggs and hosts
that lay white eggs. Parrotbills exhibited a keen ability to reject parasitic
eggs even when they were presented with less of their own eggs than parasitic
eggs. However, though, when no host eggs were present as a template,
parrotbills commonly accepted the parasitic eggs as their own.
These results support the parrotbill’s
usage of online self-referencing. In conclusion, parrotbills use the presence
of their own eggs as suggestion for distinguishing between their own and
parasitic eggs, which supports that the host employs true recognition when recognizing
their own eggs. Because parrotbills often cannot recognize their own eggs
without a template, though, they also employ discordancy.
Yang, C., Moller, A. P., Roskaft, E.,
Moksnes, A., Liang, W., and B. G. Stokke. 2014. Reject the odd egg: egg
recognition mechanisms in parrotbills. Behavioral Ecology 25(6): 1320- 1324.
I find it very interesting that in the case where parrotbills were presented with only the parasitic eggs they accepted them to be their young. As you said, that would mean that the parrotbills use the appearance their own eggs to distinguish parrotbill eggs from parasitic eggs.
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