A summary of a typical house martin season in the UK
This is a guide to a typical summer in the UK. There will be many variations but I have tried to describe an average summer from many years of my notes of house martin behaviour.
The first few house martins arrive. These early birds are mainly birds that bred last year. They arrive from the middle of the month and clearly recognise local nest sites and roost in them if they are in good condition. They are the ‘tip of the iceberg’ and often remain in low numbers until early May. Nevertheless in warm weather, particularly towards the end of the month a few pairs may form and start to breed. These early birds often experience very cold weather, especially further north- I have watched house martins in snow showers. They can often be found feeding over local lakes and reservoirs during the day, only visiting nests to roost.
In good weather more house martins arrive, more pairs form and many start building and repairing nests and laying eggs. Birds using artificial or undamaged natural nests can start breeding quickly having lined the nest cup. Poor, cool weather can push this activity back and delay the breeding season. In such weather throughout the summer house martins often have to feed very low over water, or very close to tree canopies to glean insects.
From mid May on the first time breeding birds start touring colonies or looking at new buildings searching for a place to start building a nest. These are the birds most often attracted to new areas with artificial nest cups so this is a great time to play calls. They can start nest lining and egg laying right through to late June or July.
This is also the time when you can make a big difference by maintaining mud supplies if the weather is dry. I recall one spring in Ampleforth when birds totally stopped building in fine weather. I watered the main source of mud which had dried up and they started building immediately.
Many first time breeders are still looking for nest sites, so it is well worth playing calls if you have artificial nests on your house.
Meanwhile established breeders that laid eggs in May are feeding young. By the middle of the month the first young martins will have fledged. These fledglings will roost in the nest for a while before the adults begin laying a second clutch.
First time breeders might be laying eggs or incubating by the end of June.
July sees the peak of colony activity with first time breeders and last year’s breeders all on eggs or feeding nestlings. Non breeding birds may well be visiting colonies. Fine weather often sees the martins feeding very high especially in the afternoon.
Juvenile house martins independent of their parents can sometimes be seen going to roost in trees. Fast flying groups whizz around tree tops at dusk then suddenly disappear. They enter the tree canopy very fast and often near the top so you have to watch very carefully.
You may well see non-breeding swifts being attracted to the house martin colony. They often follow individual house martins in towards the eaves and frequently land on house martin nests for a look. Last year we had 3 pairs of swifts and 3 pairs of house martins in a 7 ft section of eaves. The two species live harmoniously together.
Lots of house martin nestlings are still in nests. Some of these are the second broods of older birds. Particularly during the second half of August large numbers of house martins from nearby colonies may gather at your colony and enter different nests including unoccupied nests. Some may add nest material but do not breed, probably in preparation for next year- these pairs may roost each night until it is time to migrate. Others randomly visit nests and sometimes roost in them- some of these birds may be on passage using the nests as a temporary roost.
If you look closely many of these birds are young from this year with browner plumage and obvious pale fringed tertial feathers. Playing calls can often attract these pre migration flocks which might help you attract new birds next year? These gatherings can be quite spectacular with dozens of birds involved especially on sunny mornings.
Lots of gathering flocks are preparing to migrate. These can involve hundreds of birds. Large numbers leave around the middle of the month with some spectacular gatherings on the South Coast of England involving thousands of birds. Some late broods are still in nests being fed by adults that resist the urge to migrate with the aforementioned flocks. These late nestlings may fledge later in the month, though by then they can be vulnerable to cooler weather.
By the end of the month a small proportion of the summer’s house martins remain. You may well see straggling groups into October before finally sightings become very scarce then non existent.
House martins in 2021
We were fortunate to see our colony grow from one breeding pair in 2020(our first) to four breeding pairs in 2021. But this felt bittersweet because across the UK many established colonies saw a big reduction in numbers or a total collapse of the colony.
Our first bird, a male, returned on April 26th, joined by a few more in early May. We attracted four pairs which raised a total of six broods. We do not know the cause of the sudden drop in house martin numbers in 2021, it is more than likely the cold spring had some effect but the question is were the birds prevented from coming here by the cold or did some migrate into the cold and die? The second wave of first time breeding birds seemed to arrive as usual later in May and June, at least they did here in Gilling East. We will have to wait until May to see if there is a significant recovery this year.
We have eight artificial nest cups on our house and this undoubtedly gave our four pairs an advantage because they didn’t spend time and energy building new nests. It was a great joy to have them nesting on the house and to know that we gave four pairs the best possible chance of success in such a poor year. They shared the eaves with three pairs of swifts without any problems and on many occasions it has been easy to see that the two species benefit from the other’s company, especially in signalling the alarm when predators are near. They also share similar feeding habits, both feeding on insects high up in the air during fine weather and much lower down in poor weather.
At each house we have owned with both species nesting it has been common to observe non breeding swifts following house martins in to the eaves. House martins can attract swifts to your eaves and swifts can attract house martins to your eaves. Occasionally this was a problem as the ‘banging’ swifts knocked chunks of mud off natural martin nests with the extra force of their landings, but these nests were soon bolstered up by their rightful owners. But having house martins certainly seems to help in attracting swifts and vice versa. Last year in section of eaves just 7ft long we had 3 pairs of swifts and 3 pairs of house martins breeding.
Some artificial house martin cups are placed directly underneath or next to swift boxes and all were occupied. One is positioned so my son can watch the martins from his pillow; careful positioning can offer a great opportunity for children or adults to engage with nature. Turning the boxes to face along the eaves allows great viewing from inside.
House martin calls
I played house martin calls each year from 2018. The first two seasons saw no effect; despite having house martins nesting within 200m the calls were almost completely ignored. I had completely stopped playing them in June 2020 when a pair suddenly occupied a nest box. Soon after this two other pairs occupied nest cups for most of July until September, but only the one pair nested. The two non-breeding pairs acted very like non-breeding swifts, always roosting at night and visiting and nest building during the day but never actually laying eggs.
I often had large numbers of house martins attracted to our house and even entering artificial nests when calls were played in late August. This was exciting to watch but never saw a nesting pair the following spring. I have regularly attracted house martins to calls, but they were always enticed away to existing nesting areas- in other words attracted more by the sight of real house martins. That said, it is quite possible that the calls put our house ‘on the map’ for prospecting martins who later returned. Plenty of observers report success with calls so definitely try them from April to September. There is plenty of room for experimentation in this area. Like swifts preference for prospecting martins seems to be early to mid morning with the addition of regular midday and evening prospecting.
Here are some of my sketches from the 2021 season.
I am very glad to serve on the committee of the new group House Martin Conservation UK and Ireland. I have been lucky enough to have house martins on several houses I have lived in, all attracted to artificial nest cups. These give the birds a secure nest to return to each year and thus a head start over others which have to build a new nest. These trusting birds give us immeasurable pleasure from April to September. They linger long after the swifts have departed keeping the sounds of summer alive.
Here is a link to our website:
Please feel free to download and display or distribute the A5 flier below. Putting this on display in local shops, village halls, notice boards etc. may encourage your community to care for and enjoy house martins when they return.
Sketches of house martins nesting in artificial nest cups on our house in Gilling East, North Yorkshire.