Birds getting sociable - 16 August 2024

There feels to be a bit of a theme to the wildlife scene this week- many of our birds are making the transition towards congregating in groups in areas with good feeding, following the breeding season. This is especially true of waders, who finish breeding relatively early in the summer. We have seen varying numbers of Green Sandpiper across the reserve, with seven dotted along a ditch on Cowles Drove a few days ago, and two on the muddy western edge of the Washland this morning (16 August). Lapwing numbers are also building, with over 100 on 13 August on the Washland, but at least a few every day. Earlier this afternoon our Assistant Warden Haydn and I took a trip to the new land on Cowles Drove, where we spotted over 100 in a ploughed field (not one of ours) so it looks like this larger flock hangs around quite locally. It shouldn't be long before we begin to see the first Common Sandpiper, Dunlin, Curlew or Black-tailed Godwit on passage too- but there's no telling when this will be so if you visit in the next week or two, take a look around the muddy edges of the Washland to see what's about. 

Our Great White Egrets are beginning to assemble in numbers too- we reached a season-high of 23 this morning, which is only one fewer than our high count of 24 last Autumn- so I expect we will surpass this soon. There are breeding populations locally, such as at RSPB Ouse Washes, so we do expect numbers to rise over the years. We also had five Little Egret and six Grey Heron with them this morning, so it looked a bit like a scene from the fringes of a watering hole in Africa, with dozens of egrets looking for fish in the shallows!

 Photo credit: Some of our Great White Egrets perched in a willow tree, seen from Joist Fen on 16 August 2024. Photo taken by Haydn Fox.

We get lots of enquiries about our Common Cranes- and it would seem that they may have now left the reserve (which they see as their breeding grounds) for their Autumn and Winter gathering around the RSPB Ouse Washes reserve. We had three pairs in total (two with fledglings) and they will meet up with other families, pairs and single birds in a large social group which may reach 80+ birds- it is growing year on year in much the same way as the Great White Egret population is. There is definitely a common theme at the moment of our birds- whether they be egrets, cranes or waders or even smaller species like Long-tailed Tits, dropping their territory boundaries and becoming more gregarious and sociable. This is normal for this time of year, when the days begin to shorten and the priority now turns from raising young to surviving the colder, harsher months ahead, and making use of the natural Autumn glut of food. In the next few weeks, the abundance of berries on the bushes, spilt seed in the fields and invertebrates in the estuaries and lagoons will peak- and feeding in a group helps individuals exploit this to the maximum. Benefits include more pairs of eyes looking out for predators, keeping warmer by roosting in groups and (especially for younger birds) learning skills and habits from older, wiser birds. We will begin to see mixed flocks of tits on the reserve, perhaps with Goldcrest and Treecreeper following, and groups of finches like Linnet and Goldfinch bouncing through the air from one patch of thistles to another. 

Kingfishers have been a highlight this week with regular sightings most days from the Visitor Centre pond, Mere Hide and New Fen (from the viewpoint). We now have juvenile birds on the reserve which boosts your chance of seeing one, and a morning visit seems to improve your chance too. If you are at New Fen, keep an eye out for Marsh Harriers- there's more about now too as juveniles are on the reserve. The latest data from this year's Marsh Harrier nesting surveys are:

This data is invaluable to us for understanding how the reserve habitat management affects the Marsh Harriers, and it can feed in to future work too. We had a particularly well-marked (and therefore mature) male in New Fen North which probably accounts for the fact that he was able to find enough food to support four chicks. Overall, we had 17 juveniles fledge from 9 nests, with a total of 13 nests at the beginning of the season (so four failed at some point, which is normal for any breeding bird). As for the Bitterns, figures are less clear but I hope to include a bit more detail about our best guess for the season in the next blog. We think we had between 6-8 Bitterns fledge (there could have been a lot more, but they are cryptic and difficult to pin down). At the start of the season, we had 17 booming males on one survey date (though other dates had 10-12 boomers) and this difference just illustrates what separate lives males and females have. When males have attracted a female to their territory, and mated, there is no further interaction between them and the female will choose a nest site (often within the males' territory), build the nest, incubate the eggs and feed the chicks entirely on her own. Her choices are affected by factors like prey abundance (fish, frogs, small mammals and insects) which may have nothing to do with why the male chose to select and defend the territory that he did. It's different for harriers- males will help build the nest and supply all of the food to the nest in the chicks' early days. Only when the youngsters reach a good size does the female begin to leave them in good weather to forage for extra food.

Other highlights include signs of breeding in Brandon Fen- with two juvenile Sparrowhawks, one young Common Buzzard and a Green Woodpecker in Brandon Fen, seen by our administrator Suzanne yesterday (15 August). We have also been seeing young Green Woodpeckers on the entrance track, as well as Fox cubs crossing the track and a Stoat family on the path around the fenced meadow in July. On the Washland yesterday (15 July) our volunteer Paul also spotted a Common Tern. Last week, we had a family of four (two chicks) fishing for food up there which is a really encouraging sign. Most days there are 100+ Coot up there, 20-30 Mute Swan and sometimes a Hobby hunting for insects too. We have had sporadic reports of a Garganey, too- first from Joist Fen on 8 July, then one on the Washland on 10 July. These could well be separate birds- adults in eclipse or fully-grown independent chicks, as we expect they are able to breed here within the rushy margins of the pools. They are extremely secretive when breeding, so it is very rare to spot a family of them, but they come here to breed so we hope they manage it. Other duck species that are easier to see include Mallard, Gadwall and Teal, the numbers of which are slowly building across the reserve.

Insect Life

There is a lot to say here- but we can start with our moth trap results from this morning (16 July). Despite a little light rain we had a good trap- we had 52 species of 515 moths, without taking into account the 30-40 micro moths Haydn has yet to identify. Of that, we had 145 Latticed Heath, which was by far the commonest species. Then came Setaceous Hebrew Character, with 93, and Common Wainscot with 50. We saw the first Six-striped Rustic, Privet Hawkmoth and Square-spot Rustic of the season- a nod towards Autumn. 

 Photo credit: A big and beautiful Privet Hawkmoth, in the moth trap on 16 August 2024. Photo by Heidi Jones.

Whilst the moth trap allows us a view into the hidden world of these insects who fly at night, butterflies are the opposite- easy to see and admire by anyone during these warm summer days we are having. Comma, Peacock and Red Admiral are frequently spotted visiting flowers like bramble, Hemp Agrimony and the Visitor Centre buddleia. If you would like to see smaller species such as Brown Argus, Common Blue or Small Copper, try looking in the sunny, bare open areas around the car park and Brandon Fen, especially around flowers like Common Stork's-bill or Viper's Bugloss. Dragonflies are hard to miss too, with Brown Hawker especially common now. Emperor Dragonfly, Migrant Hawker and Ruddy Darter are all very easy to see, as is Common Blue Damselfly and Banded Demoiselle along the riverbank.

Upcoming Events

 Our events calendar for Autumn and Winter is in the planning stages now but our biggest event of the year, our Race for Wildlife, is on Sunday 20 October (11am until 2pm). We are hoping for well over 100 runners to attend and as well as being a brilliant day it is a crucial fundraiser for us. The more tickets we sell, the more we can do to help nature as all profits from ticket sales go directly into funding conservation work here at the RSPB. We offer a 5k and 10k route through the beautiful surroundings of the reserve, and our brilliant volunteers turn out in their dozens to support the event- from manning water stations, to marshalling, helping at the finish line or even just cheering on our runners and keeping them on track! If you think the Race isn't your thing but you still want to help us, then spreading the word about the event is really useful. You can copy and paste the link below into a social media post, or to send to friends.

For booking and further information about the race, please visit: https://events.rspb.org.uk/events/56788

To see all of our current events (more to be added soon) please visit: https://events.rspb.org.uk/lakenheathfen

As always, if you have any questions about the reserve, please feel free to give us a call on 01842 863400 or send us an e-mail using lakenheath@rspb.og.uk.


Written by Heidi Jones (Visitor Experience Officer, RSPB Lakenheath Fen).