What should I do if another bird interferes with a nest I’m watching?
If another bird takes over the nest, while the original birds had eggs or young in the nest, there is a specific way to report this to NestWatch:
- Summarize the original bird’s nest record and choose the outcome “Failure due to takeover by another bird.” Important: record the species that took over the nest, if you know it. Finish entering any other relevant data, and end the attempt.
- Start a new attempt for the bird species that took over. You can enter data as normal for this new nest. If the bird is non-native and you wish to manage the nest, please select the appropriate outcome when summarizing this new attempt (i.e., “Invasive Species Management”). Otherwise, native competitors must be allowed to nest as normal.
Both native and non-native species have been known to take over the active nests of other birds. The most common non-native nest usurpers in North America are House Sparrows and European Starlings. We have more information and tips for managing these species here.
Native birds, on the other hand, are protected by federal law in North America; it is illegal to disturb the nest or eggs of any native bird species. There are similar laws in other parts of the world—please check with your country’s wildlife authorities if you are unsure. House Wrens, for example, are native in North and South America, yet commonly usurp the nests of other cavity-nesting species. For this reason, some nest box landlords prefer not to host House Wrens. If you prefer not to attract House Wrens, make sure your nest boxes are far from shrubs or forests, or add more boxes to help reduce competition.
Interference is also possible from native brood parasites, such as the Brown-headed Cowbird in North America. Brood parasites like the cowbird do not “take over” a nest (rather, they lay their eggs in the nests of other birds for them to raise); therefore, you should not use the outcome code “Failure due to takeover by another bird” to indicate the presence of brood parasite eggs or young. If only young of the brood parasite species fledged, use the outcome code “Only brood parasites fledged.” If any of the host young fledged, that is a success and should be recorded as “At least one host young fledged.” Otherwise, choose another appropriate outcome code according to your observations (e.g., no eggs hatched, predators caused nest to fail, etc.). As with other competitors, native brood parasites must be allowed to nest as normal, except where the nest monitor has obtained any special permits required in order to manage them.