Crossbill (Loxia curvirostra): Colourful parrot of the plantations.
IF YOU'RE LUCKY, you will notice the tell tale signs that crossbills are nearby, perhaps closer than you think, but you'll need to be alert. A still day in Thetford Forest is best, with bright sunshine filtering through the needles of pine, larch or even Douglas fir and illuminating the very evidence you are looking for: tiny wing-tipped seeds drifting towards the ground. If it is quiet, it may be possible to hear a faint cracking sound from high up in the treetops (100 feet or more) as these stout, robust finches cut into their favourite food, the ripe cones of the Pinaceae family. They are not easy to spot though, as they calmly go about their business without paying the slightest bit of attention towards you. It's safe to say that if there were ever any bird that could leave you a stiff neck and sore back without even laying a feather on you, it is the crossbill.
To have narrowed down your search to the correct location is a feat in itself, for these are elusive birds at the best of times, with a roving and semi-nomadic lifestyle that is completely driven through a need to find a plentiful supply of seed rich cones. If a crop has failed in one area of the forest, they will move on until they find another, seemingly without any particular preference of cone type and will happily devour the seeds of larch, Scot's and Corsican pine. It is possible to stand at the base of a conifer tree, laden with ripe cones and feeding crossbills, yet not even know that they are there, such is the quiet nature of their feeding habits, only occasionally giving themselves away with a dropped cone or thin 'seep-seep' contact call. During courtship or at times of high excitement, a more vigorous 'toop-toop' is your clue to their whereabouts, distinct from the more familiar 'chip-chip-chip' flight call.
Once you are able to get a good view of these birds, you will immediately appreciate their acrobatic agility and proficiency when moving about amongst the upper limbs and branches of the trees, often using their cross-tipped bill as an extra limb, akin to a parrot in the upper tiers of a tropical jungle. On close inspection, it is possible to see the uniquely shaped bill possessed by these finches and appreciate how they specialise in eating cones, attacking the outer scales to reach the concealed seed in the manner that a burglar would use a crowbar on a stubborn, securely locked window frame.
The crossbills of the Breckland area show a preference for nesting amongst stands of mature Douglas fir and will sometimes form loose colonies in years of high activity. It is here that the female will build a nest made from twigs, lining it with mosses, grasses and even animal fir from sheep or rabbits living on nearby heathland. Once construction is complete, she will produce three to four mottle-patterned eggs and incubate them alone, for the cock bird occupies himself solely with feeding duties, providing his hen with the majority of her nourishment. All of these activities take place as early as February, with very good reason: food. Crossbills depend almost entirely on a single source of sustenance and need to know that a plentiful supply of cone seeds will be available when their chicks hatch and then fledge. If they are too late, the cones will have opened and dispensed their season's seeds, leaving the slow growing chicks to go hungry.
It is worth making enquiries at Forestry Commission Headquarters in Santon Downham as to the whereabouts of the crossbills. Their roving nature makes them difficult to locate from year to year and the variability of cone crops lends them to turning up in some unexpected locations. An ability to recognise ripe cones on larch or Scot's pine will assist you greatly but will not guarantee good views of these birds. However, if you do find a small nesting colony, make a mental note of nearby puddles; a diet of seeds is dry fodder at the best of times, making a small patch of water your best chance to see the finches when they come to quench their thirst.
Severe winters and failing cone crops on the Continent can force such specialist feeders to seek more prosperous territories, very occasionally leading to mass invasions of crossbills winging their way across to Britain. These invasions are known as irruptions, the first of which was recorded in 1251. It is thought that a similar irruption in 1910 laid the foundation for the population that now exists in the Brecks.
Displaying the twisted appendage that gives them their common name, a female crossbill pauses whilst she drinks water from a puddle. The bill is adapted to prise apart the cones of pines and conifers to release the dry seeds.
Parrotesque in appearance, a male crossbill is at his most gaudy during the late winter breeding season. Colours of individuals can range from a bright post-box red to a more subdued, smokey salmon- pink.