Fascinating Facts
The house martin is a small bird with almost metallic, glossy blue-black upper parts and pure white under parts. It has a distinctive white rump with a forked tail and, on close inspection, white feathers covering its legs and toes. Juveniles have brown crowns and the white areas are a buff grey.
House martins can be seen in towns and villages, as well as agricultural areas. The availability of damp mud is an important factor when choosing a breeding site. They feed ‘on the wing’ eating insects such as beetles and aphids. You can hear their persistent twittering song whilst they are either in flight or from a perch. Their call is a weak chirrup.
Seeing house martins arrive is always a welcome sight and often looked upon as a sign of summer being on its way. Even more so for householders fortunate enough to have these delightful creatures breeding under their eaves. These warm-weather migrants spend their winters in Africa, but come April and May, they can be seen all over the UK. The first individuals to return tend to be older birds, and these quickly occupy those nests that have survived the winter.
House martins traditionally built their nests on cliff faces but by the 19th century they had started making use of buildings too. A small number of house martins continue to use natural nest sites although in your area, it may be more common to see their small cup shaped nests under the eaves or ledges of buildings and houses.
These birds are semi-colonial, with an average group size of four to five nests. Some pairs will breed on their own while others breed in large colonies of more than 30 nests. Large colonies with groups of hundreds of nests have been reported!
Both males and females collect mud from streams, ponds and muddy puddles to construct their nests in around 10 days. It is thought that over 1,000 beak-sized pellets of mud and grass are used! The nest will then be lined with feathers and vegetable fibre. House martins will often return from their African wintering grounds to the same nesting sites each year and will re-use and repair old nests so please don’t knock them down! They are also known to make use of specially built artificial nests. Town colonies tend to be smaller than countryside ones.
Unlike many summer visitors, house martins do not always start breeding immediately after they return to the UK in April. Despite this, they still manage to raise two broods, and in some cases three. The young from a first brood have been seen helping to feed the young from later broods.
Breeding starts at around one year old. Four or five nonglossy white eggs are laid at daily intervals. This can sometimes be delayed by bad weather. Both sexes will take turns to incubate the eggs for 14 to 19 days. Once hatched, the female will brood the chicks whilst they are naked and cannot maintain their own body temperature. The chicks will leave the nest at around 20 days old. Once fledged, the young will use the nest to roost and to be fed by both Mum and Dad for several days. They can remain in the colony for several more weeks before they depart to join pre-migratory flocks.
Possible causes of the decline of house martins include less insect availability during breeding season, restricted nest site availability, limited access to mud for nest building and adverse weather conditions during migration.
House martins are one of our last summer migrants to leave in the autumn and may still have young in the nest during September, or even October.
Males often return to the colony they fledged from or close by, while females tend to settle several kilometres away.
House martins can be surprisingly robust in defending their nest, seeing off rivals and having a go at house sparrows looking to use a nearly completed nest cup for their own breeding attempt!
House Martins are thought to winter in southern and western Africa south of the Sahara. However, we know very little about their wintering areas. There has only been one recovery of a British-ringed House Martin. This was found in February 1984 in Southern Nigeria. The reason there are so few recoveries compared with Swallows, is that they do not form a communal roost at ground level where they can be easily caught.