Details of Award
NERC Reference : NE/D001439/1
Cuckoo host interactions: co-evolution and learning
Grant Award
- Principal Investigator:
- Professor NB Davies, University of Cambridge, Zoology
- Grant held at:
- University of Cambridge, Zoology
- Science Area:
- Terrestrial
- Overall Classification:
- Terrestrial
- ENRIs:
- Biodiversity
- Science Topics:
- Behavioural Ecology
- Abstract:
- In Nature, conflicts between species often involve evolutionary arms races, eg. improvements in strategies of attack by predators/parasites lead to improvements in defence by prey/hosts, leading to further predator/parasite improvements, and so on. Interactions between the cuckoo Cuculus canorus and its hosts provide a good subject for studying this process. The cuckoo is a famous cheat: it relies on other bird species (hosts) to raise its young. It lays just one egg per host nest. If the hosts accept this, eleven days later the cuckoo chick hatches first. Just a few hours old, it then ejects the host's eggs, balancing them on its back, one by one, and heaving them over the nest rim. Not surprisingly, hosts have evolved defences. One is to eject eggs unlike their own. In response, the cuckoo has evolved into genetically-distinct races, each specialising on one host species and laying eggs just like its host eggs, which the hosts are less likely to notice. Another is to attack adult cuckoos and increase the likelihood of rejecting eggs if they see a cuckoo on their nest (and so are more certain of parasitism). In response, the cuckoo has evolved rapid laying (c. 10 seconds) to decrease the chance it alerts the host. Although the arms race has led to genetic changes in cuckoos and hosts, individuals are also likely to improve their success through learning. The aim is to examine a case of learning on each side. (a) Learning by hosts: Hosts readily approach and attack adult cuckoos, in marked contrast to their wariness of dangerous enemies, such as sparrowhawks. How do hosts come to recognise the cuckoo as a nest enemy? Previous studies show that host populations isolated from cuckoos still reject eggs unlike their own, but have a much weaker response to cuckoo mounts on their nest and this does not stimulate increased egg rejection as it does in parasitised populations. These results suggest that unparasitised host populations may simply not recognise the adult cuckoo as an enemy because they haven't had the chance to learn this. We will do experiments with presentations of mounts of various enemies to colour-ringed, known-aged, reed warblers (a favourite cuckoo host) to test the following: what features of a potential nest enemy induce mobbing; whether mobbing calls attract neighbours; whether this experience leads naive birds to increase their mobbing and egg rejection when they encounter the same enemy on their own territory; whether hosts are predisposed to react aggressively to cuckoos, or whether they can be tricked into learning that a novel, but harmless, bird is a nest enemy; whether social learning can transmit enemy recognition along a chain of host territories. (b) Learning by cuckoos: We have discovered that not only have cuckoos evolved a 'well-matched egg' for their particular host species, but also a 'well-tuned' chick. Nestling cuckoos raised by reed warblers have different begging calls from those raised by dunnocks. Experiments show that young cuckoos change their tune appropriately when swapped between host nests, so they must somehow learn, through experience, how best to beg. We will study the begging calls from hatching to test whether cuckoos try out different calls and learn, by trial and error, which to use. We will also do experiments in which we broadcast various cuckoo begging calls to different host species to test whether the calls chosen by the cuckoos are the ones which are most effective in stimulating their particular hosts to feed them. This study of how both hosts and cuckoos fine-tune their responses by learning will help us to understand how rapidly enemies can adapt to environmental changes. In future, we hope to incorporate the effects of learning on the course of cuckoo-host co-evolution.
- NERC Reference:
- NE/D001439/1
- Grant Stage:
- Completed
- Scheme:
- Standard Grants Pre FEC
- Grant Status:
- Closed
- Programme:
- Standard Grant
This grant award has a total value of £141,247
FDAB - Financial Details (Award breakdown by headings)
| Total - T&S | Total - Staff | Total - Other Costs | Total - Indirect Costs |
|---|---|---|---|
| £12,472 | £81,180 | £10,253 | £37,343 |
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