|Song thrush nest with 3 nestlings|
|Song thrush nestlings - some downiness has already appeared with a few feather shafts just beginning to develop|
For example, it is widely believed that visiting a nest will increase the probability of the clutch failing. However, reviews of research into nesting success (Götmark 1992, Mayer-Gross et al. 1997) indicate that this is not the case, if the Code of Conduct guidelines are followed. Examples of some other less obvious actions that need to be taken are as follows (for a full list, see the Code):
- In case parent birds are watching, approach nests casually, as if by chance, rather than directly and deliberately - you are then likely to be seen as harmless (like a passing herbivore) rather than a potential nest predator.
- Adults are most sensitive to disturbance at the start of the breeding attempt, during egg laying and very early in the incubation period - it these times, they have invested less energy in the nesting attempt and have more time to lay a replacement clutch.
- Conversely, the parents become less sensitive of disturbance as the nesting attempt continues, but the chicks’ become more aware, and when partially feathered, the young of some species may instinctively scatter from the nest, a process known a ‘exploding’. This is adaptive when a real predator raids a nest is it gives a chance of survival for at least part of the brood, but once out of the nest the chicks are vulnerable to cold and to ground predators. Also, don't forget that chicks can only legally be handled by licensed bird ringers.
Here, the nest was unattended, the adults past the period of maximum senstivity and the chicks still too young to scatter - the perfect time to visit. After this, the adults could be seen bringing food to the nest and all three nestlings were seen to fledge. Once it was clear that the nest was no longer in use (young stay in the nest for 12-16 days), it was removed for closer inspection.
|Song thrush nest after the chicks had fledged|
If you want to know more about how to identify nests, eggs and nestlings, Harrison & Castell's 2002 guide is excellent, but do take care as noted above, and if possible join the Nest Record Scheme; information about breeding success is vital for well-informed conservation.
Götmark, F. (1992). The effects of investigator disturbance on nesting birds. Current Ornithology 9: 63-104.
Harrison, C. & Castell, P. (2002). Bird Nests, Eggs and Nestlings of of Britain & Europe with North Africa and the Middle East (rev. ed.). HarperCollins, London.
Mayer-Gross, H., Crick, H.Q.P. & Greenwood, J.J.D. (1997). The effect of observers visiting the nests of passerines: an experimental study. Bird Study 44: 53-65.