Occupied or Unoccupied?

Information gathered from historical breeding attempts, as well as direct observation during pre-operational checks, are our main means of ensuring informed decision making leading to mitigation measures.

It can be difficult to determine both ‘ownership’ and ‘occupancy’ of stick nests discovered during checks this early in the season. I am particularly thinking of medium sized nests where there can be a definite overlap in terms of habitat, size and structure. Nests for species such as Common Buzzard, Raven, Goshawk and Red Kite can all appear similar to the uninitiated and may have multiple nests within their nesting territory. Classic signs such as droppings under and around the nest do not accumulate until post- hatching, and moulted down and feathers are not always obvious, particularly early in the breeding cycle. To complicate matters further there are also key species which rely on recycling ‘donor’ nests from corvids and raptors – think Tawny and Long-Eared Owls, Kestrel, Hobby, and Merlin.

So, what should we be looking for?

• Consider all nest structures as potential breeding sites, even those that may appear initially unlikely. Use the precautionary principle of ‘ruling out’ sites rather than ruling them in.
• Be attentive to direct observation of relevant bird species in the vicinity or general area of a nest. This does not necessarily mean overt defensive/ alarmist behaviours such as calling, mobbing etc., the mere presence of sensitive species at, near, or over such sites should set ‘the alarm bells ringing’.
• Presence of stark, white droppings on the forest floor associated with roosting. This would normally be in general proximity to the nest site rather than around the actual nest itself. Such droppings are typically your earliest signs of habitual use and, by extension, possible breeding.
• Presence and accumulation of pellets (a bolus of undigested fur, bones and feathers regurgitated by the bird). This can be an important feature particularly when identifying owl sites. Again, this will often be associated with roosting in ‘general proximity to’ rather than directly related to the nest.
• Plucked prey remains anywhere within the general area, sometimes on a raised ‘plucking stool’ such as a rock, tree stump or root plate. The size and species of prey will vary so be prepared for everything from the remains of frogs and toads through virtually all small and medium sized birds and mammals including even carrion such as bits of lamb/wool etc. Plucking at this time is often associated with provisioning the incubating female rather than young and large accumulations at single locations are unlikely so even a single ‘kill’ could be indicative of breeding activity when other evidence is taken into account.

The main points to be taken from this are that signs can often be subtle in the early part of the season prior to hatching and are not confined to the actual nest location. Nests can also sometimes be used by species other than the original occupant.

If you have reason to suspect breeding activity in the form of a nest site you are unsure of and/or by seeing any of the signs described above then get in touch with someone with greater experience to assist you. Contact one of the Ecology Leads within Tilhill or a local expert(s) such as the local Raptor Study Group.

Also remember that any follow up visits to ‘Schedule 1’ species requires a relevant ‘disturbance licence’, again your local Raptor Study Group should be able to help.

Useful references:

GN18 – Birds and Tilhill Operations 

GN73 – Finding and Protecting Raptor Nests in Woodland

GN3 – Bats and Our Operations

Early species breeding efforts are already underway with remaining species on the cusp of getting started.