Threat recognition and response in an avian brood-parasite host from New Caledonia

Nest predation and avian brood parasitism are the main sources of nest failure in many passerine birds.Large predators threaten both brood and parents,whereas brood parasites pose only a danger to eggs or nestlings.The fan-tailed gerygone Gerygone flavolateralis from New Caledonia is subjected to high rates of nest predation by the New Caledonian crow Corvus moneduloides(responsible for about 20-40%of predation)and moderate rates of brood parasitism by the shining bronze-cuckoo Chalcites lucidus(parasitizing about 18%of nests),which also depredates nests that are too advanced for parasitism(13%of nests).To test if fan-tailed gerygones are able to discriminate predators from brood parasites,we presented 3 bird models at active gerygone nests:a brood parasite/small nest predator(shining bronze-cuckoo),a large nest predator(crow),and a small non-native bird(common chaffinch Fringilla coelebs),which is unknown to the gerygone,as a control.We assessed the response of adult gerygones to the presentation of each model by measuring the minimum approach distance,number of alarm calls,number of attacks,and time to first nest visit after the presentation(latency).Adult gerygones often attacked the cuckoo,approached but never attacked the chaffinch and always avoided the crow.Latency was shorter after an attack response and during brooding,but similar among models.We did not find any link between the cuckoo model presentation and later ejection of cuckoo nestlings.We conclude that adult fan-tailed gerygones discriminate between different models and respond accordingly to the level of threat but do not show awareness of parasitism risk and increase of nestling ejection rates following exposure to the cuckoo model.

Role of social and individual experience in interaction of the meadow ant Formica pratensis （Hymenoptera： Formicidae） with ladybird imagines and hoverfly larvae

The ability to recognize aphidophages is one of the key points in the protection ants provide aphids against their natural enemies. Behavior of honeydew collectors from nature （＂field,＂ control） and laboratory reared ＂naive＂ ants of Formica pratensis Retzius, which had never met either ＂mature＂ workers or aphids and aphidophages, was observed during their pairwise interactions with ladybird imagines and hoverfly larvae. The majority of the ＂naive＂ ants perceived ladybirds as an enemy at their first encounter attacking them immediately without any prior antennation. Ants seem to have a certain innate ＂enemy image＂ that lets them react very quickly to protect aphids. Hoverfly larvae were rarely attacked by both ＂field＂ and ＂naive＂ ants （〉 15%）. During tests with ladybirds ants from nature attacked them and also demonstrated the most aggressive reactions （series of bites and ＂death grip＂） less frequently than the ＂naive＂ ants. The percentage of ants avoiding aphidophages after a contact with their chemical defense （reflex bleeding and glue-like saliva） was significantly higher in the control group. Whereas the ＂naive＂ ants did not learn to avoid danger, foragers from nature usually tried to avoid negative experience and used tactics of ＂short bites.＂ Overall, experience has been proved to be unimportant for displaying key behavioral reactions underlying ant-ladybird interaction. However, accumulation of experience has been assumed to play an important role in the formation of behavioral strategy that allows honeydew collectors to drive aphidophages away with lower energy costs and avoid or minimize negative consequences of aphidophages＇ chemical defense.