A shortage of nest sites has been blamed for the decline in swift numbers
A national park is seeking volunteers to help assess the numbers of swifts returning to the area after spending the winter in Africa.
The fast moving birds often gather in large numbers to feed on insects and can sleep on the wing.
The Cairngorms National Park Authority (CNPA) said numbers were in decline in Scotland because there were fewer old buildings for them to nest in.
The survey aims to identify nest sites and buildings valuable to the birds.
The park authority said many old buildings that once provided nest sites had been demolished or renovated.
Information gathered in the park will be fed into national survey schemes.
Cairngorms biodiversity officer Stephen Corcoran hopes people will record sightings and note details of nest sites.
He said: "Previous swifts nest surveys have been extremely valuable, helping us to identify nest sites and specific buildings that are proving valuable to nesting birds.
"However, there is a real lack of data from some areas of the park and, although we want as many people as possible wherever they are to continue collecting the information.
"We especially want to hear from people in Deeside, Strathdon, Glenlivet, Atholl and Glenshee."