BTO - British Trust for Ornithology - Surveys

Arctic Skua migration: stories from the field

WEBSITEEDITOR — Fri, 13 Oct 2023 16:18:50 +0000

Where do Arctic Skuas go when they are not in Scotland? Helen and David Aiton take us through their fieldwork seasons for BTO’s Arctic Skua tracking project, which has followed these fascinating birds across both hemispheres and back. No

Helen and David Aiton

Helen and David Aiton have been members of BTO for over 40 years. Over this period, they have contributed to many BTO surveys and currently have a Breeding Bird Survey site on Rousay.

We were drawn to these beautiful birds by their plaintive calls, their stunning range of plumages and – sadly – their rapid population decline. In 1991, there were 122 pairs in our study area along with thousands of Arctic Terns. Now, in 2023, there are only 17 Arctic Skua pairs and a mere handful of breeding Arctic Terns. This trend reflects that of the UK breeding population more broadly, which is restricted to north and west Scotland and has declined by 70% since 2000.

Our fieldwork site is a triangular area of coastal moorland approximately 2 km by 1.5 km and varies from 5–115 m above sea level. We also research Great Skuas in our study area – but that is a story for another time! The aim of our long-term study is to monitor how both skua species are faring in these turbulent times.

This year, 2023, was the 10th season of our Arctic Skua productivity study, which measures the breeding success of the colony. We collect information about the number of eggs, chicks and fledged young every breeding season. Over the past 10 years, our colony has fledged 96 juvenile birds.

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A newly hatched Arctic Skua chick with its ‘egg tooth’, a sharp point on its beak that helps the chick to break the eggshell from the inside when it is ready to hatch. The egg tooth falls off the beak around a day after hatching.

Fieldwork on Rousay

Each year we visit the study area at least eight times, an effort of 16 days minimum. The island can be reached by a 30-minute ferry trip, crossing the beautiful Eynhallow Sound. Our fieldwork is made more comfortable in our old VW Campervan for overnight stays.

We locate nests at the start of each breeding season from vantage points at least 200 metres away: one person remains at the vantage point and directs the other using radios, to as many as five nests at a time. Arctic Skua nests are well hidden, so we have to use sightlines and surrounding vegetation to memorise their positions, so we can monitor them throughout the season.

Arctic Skua nests are well hidden, so we have to use sightlines and surrounding vegetation to memorise their positions.

We also use our two highly-trained German Shorthaired Pointers to increase the efficiency of finding chicks which have become more mobile and might have wandered away from the nest. It’s very important that we only undertake nest and chick finding in dry, warm weather to avoid the risk of causing any harm due to chilling.

The Arctic Skua tracking project

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Helen holding an adult bird ready for release. The geolocator is attached to the uniquely-coded orange ring on the Arctic Skua’s left leg.

Liz Humphreys from BTO Scotland contacted us in 2018, having heard about our well-established study. BTO’s scientists were keen to use geolocators to track the adult Arctic Skuas, to find out where they spent their winters, and to learn more about their migration routes. This information would help inform conservation efforts to protect this species. The work on Rousay would build on the study of Fair Isle breeding Arctic Skuas, which BTO began in 2017, and offer a comparator site. Fair Isle is roughly 30 miles from Orkney.

BTO’s Senior Research Ecologist John Callandine joined us for a week on Rousay, arriving in late May 2018. Luckily for John, we had a week of hot, dry and still weather, almost unknown in Orkney – highly suitable conditions for checking nests and catching adult birds for tagging. He was delighted that we had already located the nesting birds.

Luckily, we had a week of hot, dry and still weather, almost unknown in Orkney – highly suitable conditions for checking nests and catching adult birds for tagging.

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John (left) and David (right) place a walk-in trap over dummy eggs in the nest cup. The real eggs are safely stored in the box John is holding.

For the tagging project, we chose mostly well-established pairs of adult birds. Over the next few days, we watched the birds and waited for them to lay a full clutch of eggs. We then prepared the walk-in traps – safe structures for catching the adult birds – and left them for a couple of days near the nests, to habituate the birds to them.

Eventually, we placed the traps over the nests, to catch the adults as they walked onto the nest to incubate the eggs. To keep the eggs safe from predators while we tagged the adults, we removed them temporarily and replaced them with dummy eggs before putting the walk-in trap over the nest.

John had honed the techniques for catching birds on Fair Isle the year before, so we were a slick team! We caught 10 individual birds, two of which were a pair. As soon as the tagging was finished we replaced the real eggs. The whole process never took more than an hour.

John then left Rousay to go to Fair Isle to catch more birds, and we continued our study for the rest of the summer. It was reassuring that the birds with geolocators continued to behave normally, with most of them rearing chicks successfully that year.

Collecting the geolocator data

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Arctic Skua plumage falls broadly into two ‘phases’: pale phase (as in the bird in the top photograph) and dark phase (as in the bird in the bottom photograph). Plumage which is intermediate between these phases can also occur in some birds.

Using geolocators as a tool to understand migration routes does not provide instant gratification. To collect the data from the geolocators, they have to be retrieved from the birds, which meant we had to catch the tagged birds again to get any information at all! Innocent of the wiles and intelligence of Arctic Skuas we returned to Rousay in late spring 2019, keenly anticipating retrieving the geolocators and continuing our productivity study.

John joined us again in early June to begin the retrieval process and repeat the procedure using the walk-in traps. However, of the 10 birds we caught in 2018, only eight birds had returned, and one of the birds that did return tried to breed, but her nest failed before we had a chance to try to recapture her with the walk-in traps – down to seven birds.

Arctic Skuas share incubation duties, with both the male and the female sitting on eggs. Because individual Arctic Skuas can occur in one of two plumage types – birds are either ‘dark’ or ‘pale’ phase – we could tell the male and female apart if they had different phase plumage, what we called a ‘dark-pale phase pair combination’. But for a dark-dark phase pair combination, where only one of the pair was carrying a geolocator, we had to take extra care to ensure we were catching the right bird.

The first bird we tried to catch, a female pale-phase bird, walked straight into the walk-in trap and onto the dummy eggs – hurrah – Geolocator Number 1. After this, we thought – this was going to be easy! Alas not. That was the only geolocator retrieved during John’s visit, despite trying for the remaining six birds who all refused to go back into a walk-in trap.

Later in June, we tried mist-netting one pair that had a young chick. A mist net is a fine mesh held taut between two vertical poles, which we can use to safely catch birds by encouraging them to fly or walk into it (in this case, by placing a stuffed predator close by to the net in the hope that the adult birds would fly into the net while mobbing it) but the adults very cleverly called the chick away from the net instead. Sigh!

We were fortunate that one pair – which had had a single egg predated by a neighbouring Arctic Skua (quite common in the skua colonies) – re-laid, and had a young chick less than a week old in late July. With both adults close to their nest, we had the opportunity to try recatching them, and this time both threw themselves into the mist net at the same time! Geolocator Number 2 retrieved.

As in 2018, the colony went on to successfully fledge chicks, including that late chick.

A brief hiatus ...

Due to COVID-19 restrictions in 2020, we were not able to return to Rousay until early July, by which time the chicks were too old for us to try to catch the adults with a mist net. Again, though, it was a good year for the Arctic Skuas and they fledged at least 10 chicks.

... before fieldwork resumed

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John (left) and David (right) relaxing on the Rousay pier after fieldwork was complete.

In 2021, three years after putting the geolocators on the birds, John joined us again in glorious weather in early June. There were still four birds with geolocators breeding in the colony. We successfully mist-netted a female using dummy eggs and a stuffed predator, which she duly mobbed and entered the mist net – Geolocator Number 3 retrieved.

John and David worked very hard to retrieve the remaining three geolocators, but the birds refused to engage with the walk-in traps or the mist nets. Later in June, we tried again with the dark-phase male mate of the first pale-phase bird we retrapped in 2019 – and success! – he eventually walked into the trap and settled on the dummy eggs – Geolocator Number 4. We hoped at the very least that the birds we recaught to retrieve the geolocators this year would give us two years’ worth of migration information.

Finally, after approximately 200 hours of effort, we had four geolocators retrieved, along with six geolocators from John’s work on Fair Isle. The BTO team could set about retrieving the data from the geolocators and plotting the migration routes of the 10 Arctic Skuas. It is no exaggeration that we were all thrilled to see the results.

Migration stories revealed

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Circles show the different wintering locations of individual Arctic Skuas, each of which is represented by a different colour. Two circles of the same colour represent the wintering locations of the same bird in consecutive winters. Different birds from the same breeding colony spent our winter months off the coast of north-west Africa, south-west Africa, or the east coast of South America. The triangle shows the location of Rousay, Orkney, where the Arctic Skuas breed.

The data showed that all the Arctic Skuas travelled south via the North Sea and English Channel. Then down past France, Spain and Portugal to the coast of north-west Africa and on to their wintering grounds.

Individual Arctic Skuas wintered in different locations: off the coast of north-west Africa, the coast of south-west Africa or the east coast of South America. The accuracy of the data is roughly to the nearest 200 km so the birds are not actually on land, as can appear in the maps of the location points – they overwinter at sea. The birds that had data over two winters went back to the same area each year. Astonishingly, our pair of birds that both had geolocators went to different continents!

The work we did in Scotland will also be part of a multi-colony study of Arctic Skua wintering and migration movement involving colonies right across their north-east Atlantic breeding range – some of which was presented by BTO Senior Research Ecologist Nina O’Hanlon to the International Seabird Group Conference in Cork in September 2022 and has now been submitted for peer review. You can read more about the project’s findings in Nina’s blog.

It is rewarding to see the work we contributed to being part of a published international study. Even two years after the maps were produced, it is still deeply satisfying to be able to visualise the journeys of the Arctic Skuas when they are not on Rousay.

Since the Arctic Skua research programme was established in 2017, BTO donors have donated more than £225,000 to fund the work. We are enormously grateful for this very generous support from a small number of committed individuals. The research could not have been delivered without this funding. We would also like to thank the Scottish Ornithologists’ Club for annual grants that cover the cost of the productivity study on Rousay.

World Migratory Bird Day 2023

This blog post was created to celebrate World Migratory Bird Day (WMBD) 2023, a global event which increases the level of awareness about the threats that migratory birds are facing.

The theme of WMBD 2023 is Water, which highlights the importance of this resource for migrating birds – including for species like the Arctic Skua, which spends most of its life at sea and migrates thousands of kilometres over the ocean and across both hemispheres every year.

BTO’s Arctic Skua tracking project aims to understand where these birds spend their time when they’re not at their breeding colonies, so we can better inform global efforts to protect this species.

Discover more about Rousay’s Arctic Skuas and their astonishing migration in our other blog for WMBD 2023, written by BTO Senior Research Ecologist Nina O’Hanlon.

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Helen and David Aiton take us through their fieldwork seasons for BTO’s Arctic Skua tracking project.

1 October 2023

Where do Arctic Skuas go when they are not here?

For us, ‘here’ is Rousay, an island which lies off the West Mainland of Orkney. We have been measuring the breeding success of Arctic Skuas since 2014, and working with BTO to help track the adult birds’ migration since 2018.

13 Oct 2023

Scotland

How and why to record bumblebees

WEBSITEEDITOR — Fri, 21 Jul 2023 13:41:18 +0000

Several bumblebee species are very active at this time of year, collecting food for the next generation or busy mating. BTO’s Rob Jaques writes about watching, recording, and supporting these charming insects.

Yes

Robert Jaques

Supporter Development Officer

Robert began working at BTO in 2018 on Garden BirdWatch (GBW), where he now regularly contributes to Bird Table magazine, reviews quarterly GBW data, and manages the GBW Ambassador programme as part of his responsibilities.

Garden BirdWatch

Why should birders record bumblebees?

Many birders switch to watching and recording invertebrates during high summer, when birds are at their quietest and autumn migration is yet to really begin. Butterflies and dragonflies are the natural first port of call for most, as these large, charismatic insects are easy to see and there are plenty of resources available for identifying them.

Bumblebees are also large and colourful, but they have a reputation for being difficult to identify. While they have their challenges, with some practice and care they are certainly no more difficult than a distant sandpiper or a Phylloscopus warbler – like a Willow Warbler or a Chiffchaff – in a densely-leaved tree.

Bumblebees are a rewarding group of insects to watch, thanks to their interesting life history which involves queens, female workers and males, and quite often, their parasites. We can draw them into our gardens easily with a few of their favourite plants, and it’s worth remembering that bees are an important food source for many familiar birds. Great Tits, for example, are particularly adept at catching bumblebees!

Most importantly, however, you can monitor bumblebees in Garden BirdWatch. This gives us the means to follow their fortunes, better understand how they use our gardens and learn how to provide for them in a changing climate.

Losses and gains

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The Tree Bumbleebee likely crossed to the UK from mainland Europe.

There are currently 24 bumblebee species which breed in the UK. Some of these are incredibly widespread and easy to find, while others are restricted to particular habitats.

Some of these rarer species used to be more widespread, but due to habitat loss and other unknown factors their populations and ranges have contracted and they are now only found in isolated pockets. Sadly, a number of species have become extinct in the UK, including Cullum’s Bumblebee and Short-haired Bumblebee.

Results from the Bumblebee Conservation Trust’s BeeWalk scheme show that the numbers of our more common bumblebees have also begun to decline.

Despite these notable losses, some species are doing well. Common Carder Bees have shown increases in recent years, and in 2001 a bumblebee new to the UK was found in Wiltshire, likely having made its way across from mainland Europe. This species, the Tree Bumblebee, has spread dramatically in the UK in the past two decades, exploiting a niche (nesting in tree cavities) that is rarely used by other UK bumblebee species.

Garden records

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BTO’s survey Garden BirdWatch has been accepting bumblebee records since 2008, so we are able to see which species most frequently make use of our gardens.

Our most commonly recorded species in gardens is the Buff-tailed Bumblebee, with 21.5% of Garden BirdWatchers reporting this large and adaptable species. It is typically one of the first species seen each year – the large queens are cold tolerant, and they can often be seen feeding on crocuses, snowdrops and mahonia flowers on sunny winter days.

Buff-tailed Bumblebees are just one of seven common species that we might expect to find in gardens throughout the UK. However, if you are fortunate enough to have a garden on moorland or next to the coast you might find one of our rarer species, such as Bilberry Bumblebee or Moss Carder Bee.

With enough records, we can also use Garden BirdWatch data to see how populations have changed over time. For example, the dramatic expansion of the UK Tree Bumblebee population is clear in the increasing number and spread of records submitted to Garden BirdWatch from 2008–22.

Tips for a bee-friendly garden

Fill the garden, some pots or even a windowbox with plants such as lavenders, Salvia and Cosmos.
If you have a lawn, allow it to grow long for more bee-friendly ‘weeds’.
Avoid using pesticides.
If you have space, provide winter flowers like Mahonia for bees which emerge early in the year.

Encouraging bees

Fortunately, it is relatively easy to provide for bumblebees in our gardens. They simply need a space to nest, with most preferring to use long grass or abandoned small mammal tunnels, and a steady supply of flowers for nectar and pollen. Leaving areas of lawns and borders to grow long can help provide both, depending on which plants are present.

If you are struggling for consistent wildflowers to feed your local bumblebees, you could try planting herbs, such as mints, lavenders and Rosemary. These are long-flowering and popular with a range of bees.

It’s also worth keeping an eye out for bees in your neighbours’ gardens, to see which plants are most popular with pollinators. You can use this information to guide your own choices.

Identification tips

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This photo shows two Red-tailed Bumblebees: a male (left) and a female (right), with very different appearances and markings.

When we start to identify bumblebees, the first thing to consider is what ‘caste’ the bee we are looking at might be. Most species have queens and worker bees, which are both female, and male bees. The three castes can share similar colour patterns or be quite different from one another. For example, Tree Bumblebee castes all have a gingery-red thorax and a white tip to the tail. This is unlike the Red-tailed Bumblebee, whose queens and workers are entirely black with a red tail, with the males sporting a number of bright yellow stripes instead.

Male bumblebees share some common features across all species: longer antennae, a more squared end to the abdomen and a lack of pollen baskets (the yellowish part of a worker bee’s two hind legs, where the bee places pollen so it can be carried back to the nest). If we can identify the bee as a male, it will help us to identify the species.

At this time of year, the cuckoo bumblebees are particularly numerous. Of our 24 bumblebee species, five are brood parasites of the other bumblebees, using a suite of tactics to lay their eggs in the nest of a typical bumblebee, with the original occupants unwittingly raising the interloper’s offspring.

When searching for cuckoo bumblebees, lookout for long-bodied individuals which seem more sparsely haired, and often with different colour patterns to their host species. They also won’t gather pollen in their reduced pollen baskets, as they don’t need to feed their young.

What next?

Join GBW for free

Become more connected to nature, learn about your garden wildlife and contribute to important scientific research by joining our community of Garden BirdWatchers.

Join Garden BirdWatch today

If you are new to the exciting world of bumblebees then this overview might not be enough to get you feeling confident. Fortunately, you don’t need to know how to identify pollinators to a particular species to contribute valuable records! The Pollinator Monitoring Scheme runs Flower–Insect Timed (FIT) counts, which only require you to spend 10 minutes watching a small patch of flowers to see which species groups come to feed – for example, bumblebees, butterflies or small flies. This allows the organisers to monitor bee and pollinator populations from year to year.

At BTO, we also have resources available to help you develop your skills. We are now running training sessions on identifying garden bumblebees, which we announce through our weekly Garden BirdWatch enewsletter. Joining Garden BirdWatch is completely free, and you can sign up for the enewsletter for the latest news, seasonal features on garden wildlife, and training courses.

2 July 2023

Common Carder Bee. Edmund Fellowes / BTO

Surveys Team

Engagement

21 Jul 2023

BirdTrack migration blog (31 March–6 April)

SCMAYSON — Thu, 30 Mar 2023 13:24:59 +0000

A change in wind direction over the past week coupled with some prolonged and often heavy bursts of rain slowed migration – but some birds still made it through. No

Scott Mayson

BirdTrack Organiser

Scott’s role includes the day-to-day running of BirdTrack: updating the application, assisting county recorders by checking records and corresponding with observers.

BirdTrack

The unprecedented Alpine Swift influx came to a high at the end of last week. The true number of individuals involved is difficult to calculate as birds moved around but it is likely over 125 were seen. Over the weekend and into the early part of this week, reports fell away as birds headed back south.

The birds most likely originated from Portugal and western Spain, a theory supported by the south-westerly wind flow of the proceeding week and the fact that the initial sightings came from Ireland and then south-western Britain. A few Alpine Swifts did hang around for the rest of the week but these too will head back south in the coming days.

Early spring is a good time of year to find Water Pipits. Individuals or small groups have been reported from several locations in the past week, with a group of 10+ in Suffolk one of the highest counts. At this time of year, many of the birds are moulting out of their brown-backed and white-bellied winter plumage into their smarter summer plumage, with grey backs and pink-flushed underparts.

This makes them stand out when seen alongside Meadow Pipits. Water Pipits are purely winter visitors and within the next week or so the majority will have headed back to their breeding range in the mountains of southern and central Europe.

Reports of Whooper Swan also fell away this week, as is typical at this time of year, as birds return to Iceland for the coming breeding season. Small flocks were seen across northern Britain and some of the Western Isles as birds left their traditional wintering areas. Whooper Swans depart slightly later Bewick’s Swans, their smaller cousins, which leave in late February.

Several of the UK breeding Ospreys have already returned to their nest sites.

The last week wasn’t all about winter visitors departing for the summer months: early summer migrants did continue to arrive, even with the less-than-ideal weather. Reports of Osprey came from across Britain and Ireland with breeding pairs appearing back at their nest sites, some birds arriving within hours of the other.

A live web cam has been set up on an Osprey nest in Poole Harbour, which you can follow throughout the breeding season.

A Scottish-ringed Osprey made the headlines this week after it was spotted in Barbados. This is thought to be the confirmed example of a UK-born Osprey successfully crossing the Atlantic to the Americas.

Both Little Ringed Plover and Garganey are typical early arriving summer visitors, and a steady arrival of both species was recorded during the week. Some of the Little Ringed Plovers were seen to be displaying and going through the motions of courtship, even within a couple of days of arriving. Let us hope this year is good for them.

Don’t forget to add any breeding evidence such as this to your BirdTrack records. This information can be valuable in helping monitor the populations and distributions of some of our scarcest breeding species.

One of the birding highlights of the spring so far was the discovery late last week of a male Lesser Kestrel on the Isles of Scilly. The bird remained for much of the following week and ranged between St Mary’s and Tresco.

Gale force winds over the weekend could see some Kittiwakes turning up inland.

Looking ahead

The weather for the week ahead follows a similar pattern to the past week, with fluctuating temperatures and winds coming from a variety of directions. Strong to gale force winds are expected to hit south Wales, south-west England and the south coast of England. This could see some storm-driven seabirds pushed up the Bristol Channel and along the English Channel.

Species likely to be caught up include Fulmar, Gannet, auks and Kittiwake. Kitiwake in particular could turn up inland, so any large bodies of open water will be worth checking during the weekend and into the early part of next week. Although it is a touch early in the spring, the odd Little Gull could also be found both offshore or hawking for insects over lakes and reservoirs.

With only a handful of records each year, early April is a good time to look for white-spotted Bluethroat.

As we head into the early part of next week, high pressure will begin to build in the North Sea. Although this will bring more settled conditions to most parts of the country, it will also drag in colder winds from the east. Although this is not the best direction for spring migrants, we should still see a steady passage of swallows and martins as well as more Willow Warblers, Blackcaps and Yellow Wagtails arriving.

This is a good time of year to look out for white-spotted Bluethroat, which have a habit of turning up when the wind blows from the east. Breeding further north than the red-spotted race, the majority of records for white-spotted Bluethroat come in March into April whilst red-spotted tend to be recorded in late April and into May.

Other species to look out for in the coming days include Sandwich Tern and Mediterranean Gull. Both nest in colonies and, in the case of the Mediterranean Gull, will already be paring up and building nests. It takes three years before Mediterranean Gulls acquire their full breeding plumage and some of the first- and second-summer birds will be looking for future breeding locations. Some migrate with adult birds while others will form loose flocks and can be found loafing around larger flocks of non-breeding Black-headed Gulls.

Black-necked Grebe is a scarce breeder in England and Scotland. Now is a good time to check for both passage birds – those migrating to their breeding areas – and pairs that could potentially stay to breed. Their jet-black necks and the golden yellow fans behind their piercing red eyes make for an eye-catching grebe. However, they are secretive when breeding so repeat visits may be needed to confirm breeding.

April is a good time of year to look for Jack Snipe, which will be migrating back to Fennoscandia and Russia to breed. Any damp areas, such as the edge of reedbeds, grassy pools, or damp meadows are worth checking; looking out for their characteristic bobbing up and down might help you spot one of these cryptically plumaged birds.

Rarities that have a history of being found in early April include Pallid Swift, White-billed Diver, Night Heron, Purple Heron, Black-winged Stilt, Serin and Killdeer.

Add your records to BirdTrack

As we head into spring, your records give us valuable information about bird migration. Adding your records to BirdTrack is quick and easy – sign up today.

https://www.bto.org/our-science/projects/birdtrack

3 March 2023

A change in wind direction over the past week coupled with some prolonged and often heavy bursts of rain slowed migration but some birds still made it through.

Black-necked Grebe, Graham Catley

Surveys Team

30 Mar 2023

BirdTrack Migration

BirdTrack migration blog (24–30 March)

SCMAYSON — Thu, 23 Mar 2023 13:46:51 +0000

Spring has certainly sprung in the last week, as summer migrants have taken advantage of warmer weather with a funnel of south-westerlies aiding their arrival. No

Scott Mayson

BirdTrack Organiser

Scott’s role includes the day-to-day running of BirdTrack: updating the application, assisting county recorders by checking records and corresponding with observers.

BirdTrack

These weather conditions were responsible for the talking point of the spring so far, as over 125 Alpine Swifts were reported from across Britain and Ireland.

The first birds were reported on 13 March in Ireland, with an amazing seven birds together in Dungarvan, Co. Waterford.
More birds arrived in the week with several locations hosting two or more individuals.
The largest gathering was nine birds over Bray, Co. Wicklow on 19 March.

The influx spread across the rest of Britain and Ireland with the majority of birds seen in Ireland, and southern and eastern Britain, although some were seen as far north as the Scottish Highlands. Given the forecast, more Alpine Swifts are likely to arrive.

Alpine Swifts weren’t the only species to arrive in the last week or so. Wheatear, Sand Martin, and Chiffchaff, arrived in good numbers with many people adding them to their year lists.

All these species arrived a few days earlier than in recent years; a result of warmer weather across south-western Europe and a steady run of south-westerly winds aiding their northward migration.

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Other migrants that made their first appearances of the year included Osprey, Common Tern, Sandwich Tern, Hobby, Ring Ouzel, Willow Warbler and Sedge Warbler, and more will be arriving in the coming days.

It wasn’t all about birds arriving. Some species were departing, having spent the winter here or further south and using Britain and Ireland as a staging post along their migration routes. A steady passage of Chaffinches was seen from a number of locations, including Lowestoft in Suffolk, with a few thousand birds heading over in a matter of an hour or so.

Likewise, small groups of Redwings were found feeding up before heading out across the North Sea – their high-pitched seeep call could be heard just after dusk as they used the cover of darkness to leave the country. Redwings weren’t the only thrush species departing the UK, as during the last week small groups of Blackbirds were seen heading off at dusk. These will be Continental breeding birds that arrived here in November last year, heading back to countries such as Belgium, France and Germany.

Wildfowl numbers continued to drop as Wigeon, Pintail, Whooper Swan, and Pink-footed Goose left their wintering spots across Britain and Ireland to head to their breeding areas in Iceland, Scandinavia and the Russian Arctic. Although some will remain as late as May, the majority of these species will have left by early April and now is a good time to listen out for flocks migrating at night.

Sedge Warblers will often sing from the top of scrub in reedbeds. Look out for their parachuting song flight.

The melodic song of the male Blackcap can include some mimicry.

Looking ahead

The south-westerly winds that have dominated the weather in the past 10 days look set to change as we move through the weekend, and by the early part of next week an arctic airmass plunges down across much of Europe. This will not only see a drop in temperatures but also a switch in wind direction as cold arctic air is drawn in on northerly winds. This change in weather and wind direction will see the pace of migration slow as birds hold tight until more favourable conditions return.

This colder spell should only last two to three days and whilst it shouldn’t have too much of an effect on those birds that have already arrived, there may be some southward movement of Swallows and martins as they search for food. As we move towards the end of the week, the forecast shows a return of slightly warmer conditions and winds coming from the south or south-west.

If you are heading out this weekend there should still be birds arriving. Wooded areas are worth checking for Chiffchaffs, Willow Warblers, and Blackcaps, all of which should be singing at this time of year. These same areas may play host to Firecrests. Again, listening for their high-pitched call and Goldcrest-like song is a good way of finding these hyperactive sprites, with the males often showing the fiery centre to their crown strip as they sing.

Open areas of short grass, such as horse paddocks or rabbit-grazed meadows are a good place to look for Wheatears and Ring Ouzels. Sometimes small groups of each can be found together. The slight brown markings on the backs of male Wheatears are a good identification feature for the race oenanthe that breeds in Britain and Ireland. The Greenland race of wheatear, leucorhoa, typically arrives later in the spring around mid to late April and is a bulkier bird and has a plain steel-grey back.

Woodchat Shrikes can turn up surprisingly early compared to their Red-backed cousins.

In any reedy areas, it's worth listening out for the first singing Sedge Warblers of the year. Males will often sing from exposed bits of vegetation, such as a bramble bush or Hawthorn, when they first arrive. Their distinctive, scratchy chattering song is fast-paced. It can last several minutes and even be given in short song flights as the male rises up a few metres above the reeds before parachuting back down.

These same reedy areas can be used as roost sites for Swallows and martins, and an early morning visit could find them sat in the reeds soaking up the first rays of morning sun before they begin to feed over open water.

Whilst this time of year isn’t the classic time of year to find rare species, spring still has the potential to deliver something a little bit special. Given the current influx of Alpine Swifts, keeping your eyes skywards could prove fruitful as birds move around and new individuals arrive.

Other rarer species that can turn up at this time of year include Lesser Kestrel, Short-toed Treecreeper, Pallid Swift, Woodchat Shrike, and Western Subalpine Warbler. All these species have started to arrive back across Portugal and Spain and no doubt the occasional bird will continue northwards.

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2 March 2023

Spring has certainly sprung in the last week, as summer migrants have taken advantage of warmer weather with a funnel of south-westerlies aiding their arrival.

Wheatear, Paul Hillion

Surveys Team

24 Mar 2023

BirdTrack Migration

Amazing nesters: a journey through the bird breeding season

VIOLA.ROSS-SMITH — Tue, 14 Mar 2023 15:31:59 +0000

Bird breeding behaviours to watch out for this spring, and how to get started with nest monitoring. No

Hazel McCambridge

Scheme Support Officer & Sustainability Officer

Hazel is the lead organiser of Nesting Neighbours, and works on data collection and volunteer communication as Scheme Support Officer for several projects:

Acoustic Pipeline
Ringing Scheme
Nest Record Scheme

She is also BTO’s Sustainability Officer.

Nest Record Scheme

The mixed flocks of songbirds feeding in groups to stay safe from predators through the cold winter months start to disperse, as the urge to pair up and protect territories grows stronger. Birdsong takes on much more urgency after the quieter, colder months of feeding and roosting.

Blue Tits may be found chipping away the entrance hole and testing the integrity of a nest box, Long-tailed Tits will already be collecting moss to create a cosy dome nest and you may well have already noted a Woodpigeon precariously balancing a platform of sticks ready for a new year of nesting. Many of us will be familiar with the nesting activities of Blue Tits, which are found throughout the UK and are the most common bird to take up residence in a nest box.

We also have nostalgic familiarity with owls nesting in tree holes, thanks partly to A.A. Milne, who famously depicted Owl (an Eagle-Owl) living in a hole in a tree. However, this spring I thought it would be interesting to share some perhaps lesser-known behaviours of UK nesters as they embark on their journey through the breeding season.

Courting Great Crested Grebes, Sarah Kelman/BTO

Knowing what you’re looking at

The nesting season begins with courtship behaviours. These behaviours show that a bird is ready to mate and provides the opportunity to assess prospective partners. These courtship behaviours should not be confused with territorial displays, which are how a bird defends its territory. Nesting is a huge time and energy investment so it is important that birds select the best mate and secure their territory to ensure enough resources, such as food, are available for raising young.

Great Crested Grebes are an incredible example of how exciting mating and territorial behaviour can be. Whilst pairs will choose one another on their wintering grounds, when they return to the nesting territories their majestic and eye-catching dancing and calling builds strength in their relationship and sends the message to other Great Crested Grebes that the territory is theirs.

At the opposite end of the ‘majestic scale’, Dunnocks are small brown birds, often overlooked as they scurry along the bottom of hedges. Their courtship and mating behaviour can be rather intriguing and quite different to that of other species you may find in your garden.

Dunnock are one of few British birds where both males and females have their own territory; which lends itself to their variable mating systems. Females often breed with two or more males, but depending on the sex ratio in a population and the overlap of territories they can be monogamous, polygynous or polygynandrous.

Females can end up raising broods with young from multiple males and males can be raising broods by multiple females; the potential stories give soap operas a run for their money!

Dunnock nest in Gorse, Mike Toms/BTO

Nesting: what to expect

Nest building is something you may expect birds to do high up in trees and deep in bushes, whether it is a Blackbird nest nestled in foliage or a Blue Tit nest box imitating a hole in a tree trunk. However, nests can be discovered in all sorts of locations. Did you know that many warblers, such as Grasshopper Warbler, Willow Warbler and Wood Warbler primarily nest in tussocks of grass?

Some waders such as Lapwings also nest on the ground, but while a Lapwing’s nest is exposed and reasonably easy to spot, a warbler can be very well hidden in the grass. More commonly known species such as Robin can also nest on the ground in grass tussocks, so make sure to watch your step while exploring the countryside in the spring and summer months!

In fact, Robins are one of the most versatile species when it comes to nesting locations. From grass tussocks to the more classic ivy, they are regularly reported nesting inside car engines, boots left in the shed, tin cans and kettles – so be careful with what you leave in the garden unattended!

When it comes to egg laying, Cuckoos skip the nest building stage altogether and rely on the hard work of other birds to not only build the nest but to raise their young to fledging. Species such as Meadow Pipit, Dunnock and Pied Wagtail can be the targets of Cuckoos, with the Cuckoo chick ejecting the host species’ eggs from the nest to lay their own. The young Cuckoo can grow to be more than double the size of the parent bird feeding them!

The Goldcrest holds the record for the UK’s smallest eggs. At just 10 mm by 14 mm, Goldcrest females lay 7-10 eggs inside their tiny soft nest.

Guillemots breeding on cliff, Edmund Fellowes/BTO

Feeding and fledging

Different birds feed their young in different ways with different foods. Around two days before Woodpigeon young hatch, the adult birds start to store food in a sac in part of the digestive system near the throat, called the crop, to produce crop milk (also known as pigeon milk). Crop milk is rich in protein, minerals, fats and antibodies.

The parent birds feed the young this highly nutritious milk until they are around 10 days old, after which the adults will start to add grass and seeds to the mix. The young fledge the nest at around 33 days days old, by which time they will be eating a normal adult diet.

Taking a leap of faith and fledging the nest can be the most challenging moment of a young bird’s life, with fledglings often being coaxed by parents to take their first leap and test the strength of their wings. Not all birds actually ‘fledge’ when they leave the nest. With species such as Mallard, the young birds will stay with their parents for several weeks and are only considered fledged once they are able to leave the parents and fend for themselves.

Guillemot chicks are much the same, but rather than the mini leap of a Mallard chick from nest platform to river the Guillemot chick, whilst still tiny and fluffy at about 23 days old, must take a running leap off the side of a cliff to splash into the cold sea below. The young will then be cared for by the male, teaching them to fish and survive the harsh conditions until they are able to fly.

Tawny Owl chicks in nest box, Edmund Fellowes/BTO

Helping out with nest boxes

Many UK species make use of nest boxes, allowing us to provide a space for birds to nest when a site might not otherwise be available. These may be particularly beneficial in urban and suburban areas where there aren’t the number of trees and nest cavities available, but we can also get value from nest boxes by monitoring the activity of the birds using them.

Did you know that a nest box placed under a bridge provides a nest site for a Dipper and even seabirds such as Storm Petrels and Black Guillemots will take to nest boxes?

Building, buying and placing nest boxes

For information on building and placing nest boxes, visit our nest box guidance pages.

We also highly recommend visiting our partner, Vine House Farm, when buying high-quality nest boxes, bird houses, foods, feeders and more.

Sharing your observations with BTO

Observing and monitoring nesting birds is how we are able to learn so much about them, and these data are vital for identifying the pinch points in species’ life cycles, and developing targeted conservation action where it’s most needed and likely to be effective.

If you have a nest box in your garden, notice nesting behaviour of any species, or are interested in finding out more about monitoring nesting birds then please visit our nest monitoring pages.

1 March 2023 Amazing nesters and nest monitoring

As we transition from winter to spring, you will likely have started to notice the behaviour of birds changing along with the weather.

Sarah Kelman/BTO

Ringing and Nest Recording Team

16 Mar 2023 no