Black noddies employ a variety of visual displays to attract mates and in agonistic interactions. Displays include “nodding,” “gaping,” “foot-looking,” “head-shaking,” “bridling,” “chin-up,” and “appeasement.” Many of these visual displays are used both in agonistic interactions, as when directed aggressively at an intruder, and in mating interactions. For example, nodding occurs when an intruder is approaching and also when a mate approaches. In the former context it is used to drive the intruder away, in the latter context it is used to greet a mate. Bridling – which involves forward and backward movements of the head, accompanied by opening and closing of the bill – advertises territory ownership to both mates and intruders. Appeasement displays are usually by juveniles, who point their bills downwards to avoid an aggressive interaction. This is similar to foot-looking, which also is used to avoid aggression.
Adelie Penguin |
Government evidence of impact of climate change:
IUCN Red List Assessment, Pygoscelis adeliae
These projected decreases may only commence after a warming of 2.0 C above pre industrial levels has been reached the projected overall global trend will potentially be positive before this point (D.
It should be noted that modelled projections in response to climate change; with associated inherent uncertainty; suggest that populations could decrease north of 70 S after the mid 21st century (Ainley et al. 2010; see also Cimino et al. 2016a); and such a change will necessitate a future re examination of the AdÃ©lie Penguin s status.
Results of computer modelling work suggests that the net overall increase will continue in the near term; but that net population change may reverse in the future if climate change continues on its current track.
During the summer; nesting habitat in the Antarctic Peninsula has been affected by an increase in the incidence of severe snowfall (Fraser et al. 2013; Cimino et al. 2019); which is consistent with climate models (Turner et al. 2007; Ainley et al. 2010).
On the basis of this and more recent modelling (Cimino et al. 2016a); as well as continuously improved understanding relating to climate change impacts (e.g.
Fraser et al. 1992; 2013; Trathan et al. 2015; Ropert Coudert et al. 2019); it will be vital to periodically review population responses to ongoing climate variability and change.