The lamb head-butt incident is recorded in an official report
A lamb was seen head-butting a golden eagle, one of Scotland's largest birds of prey, according to a new report on island birdlife.
The incident is included in the 10th Outer Hebrides Bird Report, which was funded by Scottish Natural Heritage.
The incident involving the lamb and the bird of prey was recorded at Baile Ailean on the Western Isles.
Other unusual behaviour included an immature golden eagle running along the ground chasing after rabbits.
SNH said the head-butting was added to an observation of a young eagle. A spokesman said older sheep, including pregnant ewes, have been seen taking the defensive action in the past.
The 240-page report contains information about the area's resident and visiting bird species, gathered over two years by bird experts, enthusiasts and local people.
LAMB VERSUS EAGLE
Lambs and adult sheep often head-butt in play fights or, in the case of rams, to assert dominance
There were 7.4 million sheep on Scottish farms at June 2007, mainly consisting of 2.9 million breeding ewes and 3.6 million lambs, according to Scottish Government statistics
Government figures also show there is between 0.5 and one sheep per hectare of agricultural land on the Western Isles
The golden eagle is Scotland's second largest bird after the sea eagle
The RSPB estimates that there are 442 breeding pairs in the UK
The birds of prey feed on birds and mammals.
SNH area manager David Maclennan said: "This publication does a great service for the islands by recording the behaviour and movements of different species of birds, including those exceptionally rare and unusual visitors which draw bird enthusiasts here from all over the UK."
The study covers the populations and movements of all the islands' resident birds and exotic visitors across the four seasons.
It has detailed individual records of sightings and photographs contributed by ornithologists, amateur birdwatchers, crofters, fishermen and tourists.
SNH said the book revealed "fascinating insights" into the struggle for survival between birds and animals throughout the islands.
The lamb head-butt incident was recorded in 2006.
Migratory and rare visitors to the isles included an arctic tern from the Democratic Republic of Congo, a woodcock from Russia, sandpipers and whooper swans from Iceland and storm petrels from County Mayo.
One dunlin left the balmy shores of Setuba in Portugal to head for Stinky Bay, Benbecula.
The report also noted the earliest ever sightings of snowy owls and the arrival of two colourful hoopoes from sub-tropical climes.
New arrivals to the islands included a pair of Arctic skuas hunting ringed plovers, a sighting of an isabelline shrike at Brue, a pine bunting at Carinis, an olive backed pipit at Port of Ness, a Pallas's warbler at Loch Eynort and a Wilson's phalarope.