Wednesday, 31 March 2021

Anting Carrion Crows

I've wanted to film crows anting for quite a while. Anting is a behaviour carried out by a range of birds (I dealt with Blackbirds anting in a previous post), but it is rare to observe it. Anting can be active - the birds picks an ant (or ants) and rubs it on its feathers - or passive - the bird allows the ants to climb onto its plumage. The behaviour involves distinctive movements such as sitting close to the ground or partially opening the wings and tail dragging. The bird movements on top of the ant's nest or direct disturbing of the nest will also encouraging the ants to come out of the nest and climb over their feathers, as anyone who has had a picnic on an anthill will attest.

A Carrion Crow anting at my local park. 27/07/2016.

 The first time I watched anting behaviour in crows I was driving, waiting on a red light. It is a very distinctive behaviour, but I had no chance for a video or a photo! I have seen it a few more times, but didn't get a good video of it. Today, as I got out of my car I noticed the local pair of crows on the verge opposite. I used the car as a hide and filmed them. First, one of them first seemed intent in getting some nest lining material, but the other went to the base of a tree trunk and pecked, and pulled some vegetation from around the tree. Then it pressed its body against the ground. The second crow joined the first and both enjoyed an 'anting' session.

Watch both clips and a clip of the ants nest:

Why anting?
It might be surprising, but is still unclear why birds carry out anting behaviour and there are a range of hypotheses. Some claim that it is some form of feather maintenance. Species of ants that eject formic acid (Formica, Lasius and Camponotus) as part of nest defence are preferred for anting. Formic acid has insecticidal and acaricidal properties. One of the first hypothesis is that the formic acid kills or repels bird ectoparasites such as feather lice or mites. This has had some support. In the summer of 1943, in Transbaikalia, Dubinin killed four Blyth's Pipits that had been anting, counted all the feather mites and checked the mites behaviour. Many mites were already dead and a total of a third of the mites died over the next 12 h, and the rest seemed very mobile. The birds feather smelled very strongly of formic acid even 12 h after the shooting. The control for this experiment were four pipits that hadn't been anting. Only 0.9% of the mites died after 24 h, and they stayed more or less immobile. However, other experiments tested this hypothesis were inconclusive.
Another hypothesis draws on the formic acid has anti-bacterial and anti-fungal properties, and could be beneficial to keep in check bacteria and fungi that feed on feathers. Although the experiment showed that pure formic acid inhibits feather bacteria and fungi's growth, the results were not conclusive when more natural doses were used that reflected ant's formic acid content. An ornithological enigma!

More information

Morozov, N. S. Why do birds practice anting? Biology Bulletin Reviews 5, 353–365 (2015).

Tuesday, 19 January 2021

Mute Swans leaving home

There was a news item yesterday regarding a Mute Swan that had crashed through someone's bathroom window. The swan was treated for cuts and taken for further treatment. The photos suggest that this was a young mute swan. What was it doing to crash in such a way?

Young leaving home 

This time of the year young Mute Swans will be leaving their parents' territories, in search of new homes. Cygnets share their parents territory for a few months, but as the parents start preparing for a new breeding season, the male, called 'cob' becomes more and more intolerant of his offspring, busking to them and trying to keep them out of the water. This blog post was prompted by the arrival of a young mute swan to my local patch, which I saw this morning for the first time. It has possibly dispersed from a nearby lake, where they have bred this year.

A newly arrived Mute Swan at the drain today.

Parents vary in their tolerance to immature swans in their territory, or this may depend on the size of the lake, possibly smaller territories may prompt cobs to chase their offspring earlier. One pair in a local park has two batches of young, the oldest were being chased on Saturday out of the water by the cob.

26th December 2020. Adult pair of swans chase their yearling outside the water.

Cob busking to young, followed by the pen.

Fly practice

Swans are one of the largest flying birds. They are also not amazingly manoeuvrable, and collisions (for example with electric lines) are one of the main mortality causes in swans. Taking off involves paddling on the water while flapping wings, they need a clear length of water to do this and then upon starting their flight they will need to fly up so that they clear any obstacles such as trees and houses on their way. 

Mute Swan in flight.

Watching swans in my local area, I've become aware of practice flying in which young and adults participate. This activity may help the young acquire key flight skills, taking off, landing and strengthen their wings  A short chase by the male may end with several members of the family flying along the lake, to land at the other end, but I've also seen lone young practicing when alone. There is a very good description of practice flying in the blog Swan Life.


Cob encourages young to fly. I described the behaviour in my Wild at Hull blog on the 8th December:  "As I got to the lake I saw the Mute Swan family gathered on the north edge of the lake. The adult pair had their two yearlings, born in 2019, and three young born in spring 2020. Usually swans chase their young away from their territory in the autumn, but this pair tolerates their young for much longer, probably because of the large size of the lake and plentiful food. The cob, however, was all fluffed wings and lowered head, a behaviour called 'busking' to one of the two older young. After a short chase, the young started flying, followed by a younger sibling and dad, and all three flew to the other end of the lake. I watched this happened three times while I was there. The swans only needed to drift on the wind to the top of the lake, and then take advantage of the gentle head wind for an easier lift. They yearlings might be getting ready to finally leave their natal lake, practicing taking off and landing".

Another clip of the 'practice flight' next. This is not a take off that failed, the trees and the end of the pond make it impossible that the swan would be able to take off in this direction. Practice flying and landing seems to be the motivation behind it. Note the feet propel the swan over water increasing speed and lift, and are also key to brake when landing.


More information

Collins, R. Sex Differences in the Movements and Mortality of Mute SwansWaterbirds: The International Journal of Waterbird Biology 25, 157–161 (2002).

Frost, D. (2008) The use of ‘flight diverters’ reduces mute swan Cygnus olor collision with power lines at Abberton Reservoir, Essex, England. Conservation Evidence 5, 83-91.

Birkhead, M. and C. Perrins (1986) The Mute Swan. 

Monday, 4 January 2021

Ice-breaking Mute Swan

The ponds and lakes in town are all covered on ice after the last frosts. The other day I watched as part of a family of swans landed on ice on their lake, the young walking tentatively on the slippery ice. Today a pair of swans reached the edge of the ice and the cob seemed determined to move on. It pushed its chest onto the ice and broke it, moving forward each time. I noticed how after each break, it did a tail shake, as they often do after landing. I wonder if the swan feels like it is in unchartered territory and is nervous while breaking the ice. Tail shaking is something waterfowl do after an exciting event (mating, landing). The cob fed under where the ice had been, but then it decided to turn round to its partner.

Cob mute swan ice breaking.

Often lakes that have swans have some open water, as the large, heavy swans are able to break the ice. If they can't and the lake becomes fully iced over, then all waterfowl leaves in search of some open water. 

These are some photos of a mute swan family in a different lake.
Initially one of the young was on its own.

Its family had landed on the other side of the lake, on the ice, and it flew towards them.
The young was then keen to return to the open water.
The pen was happy to stop to preen and rest on the ice.

Tuesday, 8 December 2020

Carrion Crows feeding on Plane Tree fruits

This morning I took a walk near a local park. On a square lined with Plane Trees, some pollarded, a flock of Goldfinches fed on the bauble-like fruits, often hanging from them acrobatically, as they often do.

Then I noticed the crows. They flew to the tip of the branches, where the plane tree fruits clustered, once they gained their balance they moved to the tip of the branch, and picked on the fruits, pulling at their stem. Then they purposefully hanged down from their legs, then only one leg while holding the fruit on the other and attempting to break the stem. What complex thing to do! Some of the fruits had frayed stems, like they had been chewed a few times. If a crow breaks the stem but drops the fruit, the other crows will be quick to go and steal the price. I didn't see this, but I did see chases and close guarding of the fruit by the owner crow, often flying to a safer place holding onto it.

All three crows did this, often the three of them hanging from branches at the same time. At least twice I saw they were successful, and then they flew with the fruit on their bill, once transferring it to their feet before landing and starting breaking the fruit open for their seeds. I'm always amazed at crows, I have covered how they crack mussels and periwinkles at the beach.

Today's behaviour, however, really topped it up. Were they copying the Goldfinches? Crows are always to the alert, they must have noticed the Goldfinches feeding on these fruits and had a go at getting them!

This is a video made with three clips I took from them

And a few photos of the behaviour.

Hanging from one leg, holding onto the fruit with the other.

Crow with its prize.
The pink gape suggests this is a young crow, feeding on the plane fruit. I wonder if this is a family, with the young copying the adults in learning this skill.
I'll be very interested to head from anyone that have seen this behaviour in their local crows!

Sunday, 8 November 2020

Herring Gull pair long call duetting

You have probably seen Gibbon pairs duetting in nature documentaries or videos. It is a territory display that shows how the pair is well bonded, and the turn-taking of the duetting is amazingly precise, the pair alternating calls to produce a single 'song' that advertises their presence and ownership of a territory. But you don't need to travel to distant tropical jungles to witness pairs duetting animals. Herring Gulls do it all the time. Because their long call is so familiar we tend not to pay much attention to it, but I was made to stop a couple of days ago when a pair landed on a chimney stack opposite my house (above). One of the pair seemed intent on long calling, and started to call, followed each time by its partner. Long calls become commonplace during the breeding season, when pairs defend territories or food, as it appears to have an aggressive function. Here is a sonogram of it. The gull starts calling with the neck pointing down, the calls well spaced, then the calling becomes faster in a staccato and the gull stretches its neck and points up and then the call dies in intensity. In 'The Herring Gull world, Tinbergen describes the call, but not the fact that it often occurs in pairs, there the pair message is not to each other, but to other gulls. The duetting has also been described in other gulls, like in the Western Gull.
A pair of Herring Gulls with their two young duet on a roof in Filey.
Often, one of the pair starts the call, and the other joins in and they end the long call together, necks stretched, bills pointing up.
Why do gulls long call? They seem to do it when they have asserted their ownership of something (food, for example) or finish a squabble, or sometimes the whole Herring Gull colony calls and pairs joins together. I'm surprised I've found so little about this amazing behaviour other than anecdotal references to it, but this is a wonderful photo of a pair duetting.

More information
An article on long calls in various gull species. Earbirding.

Sunday, 18 October 2020

Pink-footed geese commute

One of the highlights of my bird year is to first hear and then see the wavy skeins of Pink-footed Geese flying over from their summer breeding quarters in Iceland and East Greenland.

This morning, I headed to my local park to carry out the Wetland Bird Survey. I counted the Greylag and Canada geese flock, the Common Gull flock, all recently arrived, and the resident Mallards and Moorhens. But al through, there was a beautiful background noise of calling Pink-footed geese. Flock after flock flew over, their arrival preceded by their echoing calls. Most were going north, 1500 of them.

You might be puzzled to see these geese flocks flying north or east early in the morning, how can it be that they are not going south? The reason is these birds are wintering or staging their migration in the Humber Estuary. What we are watching is their daily commute, in fact, their morning rush hour! Every night, the flocks gather to roost Read's Island and Whitton Island in the upper Humber estuary, where they are safe from disturbance and predation. At day rise, the birds fly to fields on Holderness or the wolds to feed, favouring fallow fields, or the spilt grain in those fields still to be planted, and also left-over potatoes! A similar movement happens towards Lincolnshire.

The Pink-footed geese population suffered strong declines in the 20th century, but it has been steadily increasing in the last couple of decades. The increase was followed by a renewed use of the Humber Estuary for wintering and also as a staging post on the way to Norfolk. UK coasts and estuaries now hold a sizeable amount of the total wintering population of this geese species, estimated to be about half a million birds.

With the constant daily movement, it is unavoidable that a few stragglers will separate from the flock. They call pitifully when trying to catch up. Many will eventually find the flock. Some others, which could mainly be young birds which haven't learned the route, may be disoriented and join a Greylag flock, as has happened several times in our local parks

More information

A Humber Goose spectacular. RSPB Blog by Pete Short.

Mapping the Pink-footed Geese.

WeBs survey results.

Tuesday, 10 March 2020

Colour-ringed Waxwings

I went to see the Hessle waxwings this morning, where a flock has been present since last Friday. Straight away, I saw two photographers looking at a tree. I soon joined them and the 18-strong flock was there, in a small street-lining cherry tree, facing the strong westerly wind. The light was beautiful compared to my previous Waxwing sightings, most of the time in the depths of winter. The birds were quite mobile, trilling and moving from tree to tree before descending to the unlikely source of berries this time of year: hawthorns.
No supermarket car pars, but car dealerships this time.
The 18 strong flock. 
Berries, what berries?
Probably most hawthorns in the country were stripped of berries long ago. Not these. The leaves of some of them sprouting amongst last year’s crop of berries. The reason for the late berries could lay in the location of this hedge: a very narrow strip of land between the A63 and a busy local road on an industrial estate. Every time the waxwings descended to feed, roaring trucks on one side and fast delivery vans on the other, I feared for their safety. Photos don’t really convey the feeling of being there, the noise of the road and the wind, the feel of the acrid stench of the traffic fumes at the back of your throat. This stressful food location has probably kept the local thrushes and Woodpigeons away.
On the hawthorn: berries and fresh shoots.

Colour rings
Two of the waxwings had plastic rings with different colour combinations on their legs. The yellow plastic over metal of their right legs indicate that both birds are part of the 2019 ringing scheme by the Grampian Ringing Group. In fact, information supplied by Raymond Duncan from the Grampian ringing group indicates that both birds were ringed on the 7th December 2019, in Aberdeen. One of the birds, a female with white, black and red rings stayed put until the 5th of January at Aberdeen, the other, a male with light green over dark green and dark green ring was found in Thirsk (N Yorkshire) on the 30th December and 3rd of January. Waxwings move towards the UK at the beginning of winter, in large numbers when the berry crop in Scandinavia is poor, what is called irruptions, and then they move south and east through the country. Is it coincidence that both birds are together in Hessle? Although social birds, Waxwings are not known for forming strong individual bonds when they move about during winter. However, there are reports of the same birds returning to favoured spots in different irruption years, so the same individuals may meet again in these Waxwing hotspots.

The Grampian Ringing Group has many years of experience colour ringing waxwings: they have colour-ringed thousands of waxwings for over thirty years. This winter, their dedication has paid off with 100 ringed waxwings and some resightings across the country. Their blog is a treasure trove from everything waxwing including how to sex and age them. Resightings of colour ringed birds, particularly when the colour rings and their position can be ascertained, are crucial to follow the movements of Waxwings without need to recapture them.
The male was ringed in Aberdeen in December.
Female also ringed in Aberdeen in December.
Males, females and ageing
Waxwings of different sexes and ages appear similar at first sight, but they are subtly different. Examination of their plumage pattern can actually be used to age and sex them. Adults have their primaries edged with white and bright yellow, forming a ‘hook’, while young individuals have only one side of the primaries lined with white or pale yellow. When the wing is closed this forms a single line. First winter immatures also have a shorter crest. The ‘bib’ is larger and sharper in males, while the bib edges are diffuse in females. The yellow terminal tail band is wider in males. Males have over 6 waxy red feather tips, and these are longer in adult males, but there is some overlap between sexes. Females have a small number of smaller waxy tips. Some of these features are visible in flight, so you may want to have a go at sexing and aging your waxwings from photos.
The diffuse edge of the bib indicates this is a female.
After watching the Waxwings for a while, I went to their old haunts in Priory Park at Hessle. Trees lining the road between Sainsburys and Aldi supermarkets have been removed, but their favourite berry trees, rowans, are still there, of course, there wasn't a single berry left!