House Martins in Cardiff Bay

by Paul Seligman

Adventurer’s Quay

In 2008, I noticed that there were House Martins nesting in Adventurer’s Quay, a gated development opposite the office where I worked. Subsequently, I managed to gain access during the nesting season at least once each year.


House Martins

My criteria for counting a nest as ‘this season’ are that it looks in good repair and preferably has fresh droppings, feathers or faecal sacs underneath. Of course, if one sees birds entering or leaving or can see or hear the young, then it’s certain (and I separately record the number of definitely occupied nests). But you can’t wait by each one till this happens on dispersed sites of this size. The maximum number of current nests each year is shown in the following table:

2008 2009 2010 2011 2012 2013 2014
7 21 8 15 12 10 11
Maximum ‘current season’ nests at Adventurer’s Quay

The annual figures are not strictly comparable because the survey was not conducted at a fixed time of year. For example, in 2008 and 2010, I only visited in April when a number of nests were still being constructed, which I didn’t count. The final numbers were probably closer to the other years. Conversely in 2012, I found 13 nests on a first visit, but later in the season there were only 8 left, almost certainly due to deliberate removal of nests near windows.

I persuaded Cardiff Council, through the Biodiversity Partnership, to produce a Love your House Martins and leave their nests alone leaflet, which I delivered to every address in Adventurer’s’ Quay in 2013. It’s hard to measure the effect of this, but one hopes it does some good.

Other Sites

Walking around the Bay earlier this year, I recorded a few House Martin nests in Penarth Marina and Windsor Quay. Judging by the number of birds flying around, I was sure I would find more if I surveyed these two sites in detail.

Having checked that there were no known records of the numbers of nests at these sites, I surveyed them in August. Both areas take a long time to walk round every side of every building, as far as is possible (the nests can be on sides facing any direction). On both developments, residents have been offered the option of having artificial nests put under their eaves. I saw quite a number of these but only two I could say were definitely in use, and a couple more in possible use (which I didn’t record), for example showing some slight marks of droppings. Some evidence of nest destruction or removal was seen at both sites and in 2015 I will try to ensure leafleting of all the residents, although this will take thousands of leaflets.

Individual nests could be quite isolated, perhaps 50m or more from the next, or they could be close to or touching others. ‘Double’ nests are quite common, triples occasionally seen. In Penarth Marina, there were 7 nests on one short stretch of roof (mostly over one window – showing house-holder tolerance).  One building had 16 nests.

At Penarth Marina, I found 78 nests that were in good condition, 13 of which I saw being actively used. In the Windsor Quay – Seager Drive development in Grangetown, I found 19 nests, and saw 3 being used. At both sites there were enough martins flying around to suggest that the number of nests I recorded was realistic. I would estimate that the numbers of nests I recorded are a slight underestimate as some dwellings with steep roofs overhanging the eaves could not be fully examined. I haven’t checked every possible building around the entire bay but I think these are the main sites. If anyone knows of more, please get in touch.


Recording similar data each year is useful. It’s even better if the methodology is consistent (time of year, criteria for recording). Recorders deciding to make any survey should consider such details in advance!

As the House Martin flies, these 3 sites are very close and they can certainly all be seen from each other’s windows (or roofs). I therefore suggest that the three sites surveyed constitute a super-colony. In 2014, this comprised at least 108 nests. It would be great if we had ringing data to establish how much movement between the sites took place each year. It is possible there would be more nests if some weren’t deliberately removed each year, sometimes after eggs were laid. However, I don’t know if birds that lose a nest early on simply rebuild elsewhere; there certainly appears room for more nests at all the sites.

The buildings themselves were mostly built in 1998-2002, demonstrating that House Martins will readily adapt to new locations if the construction is suitable and are comfortable nesting on uPVC, as well as more traditional materials.

I’ll try to survey all these sites in future years close to a regular date, such as mid-July, to see how the trends develop. It seems to me that counting apparently active nests is a good way to estimate the actual number of breeding pairs of obvious colonial nesters like House Martins (compare the long running Grey Heron survey). A few years ago, I suggested to Glamorgan Bird Club that nest numbers of this species were reported in the Annual East Glamorgan Bird Report and this is now being done. Of course, this requires known nests to be counted and reported – can you help?

Paul Seligman
t: @PaulSeligNature

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