Although declining in many localities the house martin remains a familiar bird. Its white rump, white feathered legs and shorter, less forked, tail distinguish it from the swallow.
The house martin feeding zone is higher than that of the swallow. It can often be seen 'towering' after insects in association with swifts high in the air. Gliding and stalling, diving and climbing it spirals overhead displaying great grace and mastery of flight.
On occasions house martins are attracted to hot-air balloons. The birds circle just above each balloon maybe gaining lift or free-ridings as in a thermal.
House martins breed over a vast area of the Palearctic region from the Atlantic towards the Pacific and as far north as arctic Scandinavia. Before man provided shelter in the shape of overhanging eaves, martins were cliff and cave dwellers. In remote mountain regions they occur at altitudes up to 14,000 feet. In southern Europe there are enormous colonies, the nests overlapping and forming huge tenements.
House martins do not often settle on the ground except when collecting pelts of almost liquid mud for nest construction. They are then very approachable. Both birds work at nest building, but before this begins there is much play.
A bird will fly up and dab a pellet of mud on the wall, then cling with head turned. Twittering an invitation to its partner who will settle alongside. Spreading wings they then drop performing a graceful arc before floating off for aerial courtship.
The birds soon took advantage of newly constructed motorway bridges colonising them within a season of their completion. This despite vehicles thundering a few feet away. Suffolk house martins discovered the advantages of building nests under circular lamp column shades. At its peak, the colony numbered almost 60 nests built under a dozen shades.
Even more resourceful are house martins nesting on ships. A pair once nested aboard a ferry travelling eight times a day between Copenhagen and Malmo in Sweden. The nest was situated on a ledge beneath a bulkhead close to the port rail.
The crossing was 15 miles in length. Following publication in British Birds magazine further occurrences came to light. Another Danish car ferry engaged on an internal route of some eight miles and a journey of 45 minutes (making a round trip of two hours) held up to nine house martin nests for a period of over a decade. In more than one year all the broods successfully fledged.
The adult birds visited the ferry only at the terminus, entering the vessel immediately the bowgate opened. The kindly ferry company deliberately did not use this ship at the beginning of each season because of the nesting martins.
In cold, wet weather early in the breeding season up to 14 house martins have been recorded sheltering in a single old nest. Many survive by this behaviour.
During nest building, disputes may arrive through the theft of both mud and lining materials. Parent house martins share brooding and feeding duties. Young from the first brood are known to feed later nestlings.
I have noted young still in the nest during the last week in October. After leaving their mud homes the young congregate in flocks, sun-bathing on southfacing roofs and roping the wires in company with swallows.
More than one mystery surrounds house martins. Where do they roost when not at their home colonies?
It seems likely the majority sleep in trees. Watch a flight of house martins during the hour before sunset. All fly high and at times binoculars are needed. Ten minutes or so after sunset all suddenly become excited and flight is accelerated for no apparent reason.
Then all come sweeping down the sky to treetop level before vanishing into high foliage at top speed. And the same trees may be occupied over several weeks.
As the time of autumn
departure approaches, aerial exercises are intensified, the martin flocks
wheeling restlessly. Then one morning the cables are deserted. The long
journey through France and across the Sahara has begun. Another house
martin mystery when in the African tropics is the scarcity of observations
considering the great numbers which are still involved. Perhaps the answer
is a high altitude lifestyle?
.By Michael J Seago