BREEDING SUCCESS for one of Scotland’s rarest birds of prey has been found to be linked to the age of the adult male bird involved.

A new report published by NatureScot found that the age of parent birds, availability of prey and land use, are key factors in the success of a nest in adding to the population.

Hen harriers have a low survival rate for young birds, and the project showed that where the reasons for failure could be determined, all the nest failures were due to natural factors including predation by foxes and other birds.

These findings were a result of five years of camera evidence on 28 estates participating in the 'Heads Up for Harriers' partnership project – images were taken from 52 hen harrier nests, and 37 of these had permanent cameras installed.

It was revealed that there was a 91% success rate when males were older than one year, irrespective of the age of the adult female bird.

The report also found that nesting attempts and fledging success were higher during warm, dry spring weather, with wetter weather having a negative impact on both the harriers and availability of prey.

Birds account for 89% of prey for hen harriers, predominantly Meadow pipits – however they rarely prey on grouse, which only account for 5.6% of prey.

Over two million hen harrier nest camera images were meticulously studied to reveal harrier behaviour and factors impacting their survival. While the majority of estates have some game shooting interest, analysis indicated that harriers fare best on those estates with no shooting interests, with more breeding attempts, nesting success and higher productivity recorded on the majority of non-sporting estates.

Chair of the 'Heads Up for Harriers' Group, Professor Des Thompson of NatureScot, said: “Hen harriers continue to struggle in Scotland and they remain a rare species, although Scotland holds by far the majority of the UK population with 505 territorial pairs. This report shows that almost half of breeding adult female birds are four years or older and 87% of male birds are older than one year, despite the females being capable of breeding much earlier. This indicates a high turnover of young birds, and while the report does not speculate as to the reasons, this is a worrying statistic.”

Report author, Brian Etheridge, added: “Some fascinating patterns in hen harrier breeding habits have been identified, such as a tendency for nesting on westerly facing slopes, with an increasing preference for nests in higher areas, and the low occurrence of grouse within the sampled 500 prey items. This information should help land managers better cater for nesting harriers, while providing reassurance of the limited impact on game birds.”

For the full report, see