Redpolls and Goldfinches feeding on Sycamore aphids

 I'm used to finding Lesser Redpolls in the coldest days of winter, when small groups feed quietly on birch catkins. Learning their cheerful 'chi-chip' call, sharper and less liquid than Greenfinches, has helped me detecting them as they move around the city. I was surprised to hear their flight calls amongst a flock of roving Goldfinches at my local cemetery, a misty but mild morning. I trained my binoculars high up on the Sycamores and spotted them, apparently gorging on the last fat sweet aphids still under the Sycamore leaves, together with the Goldfinches. Some Chaffinches and Blue and Great tits were also on the sycamores, but I'm more used to these species feeding on insects. The distance and the poor light didn't make for great photos, but I was pleased to record a behaviour I had never seen before for both Redpolls and Goldfinches.

Sycamore aphids.

Redpoll gleaning sycamore aphids.

Lesser Redpoll.

Lesser Redpoll.

Goldfinches and sycamore aphids.

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!

What are goldfinches doing on tree branches?

At this time of year I often see Goldfinches appearing to feed high on tree branches, often sycamores. It is hard to see what exactly they are doing, but definitely there are no seeds involved, it looks like they are pecking the bark or possibly lichens. I checked and they were not holding seeds under their feet (as they often do) or wiping their bills clean. They appear to peck the surface of the branch. I managed to photograph one that appears to lift and hold a bit of bark with lichen on top (top shot).

I am very curious to know what they are doing. During the breeding season Goldfinches use lichen to camouflage their nests, I only see this behaviour during winter. Has anyone seen this? Please comment! Some more photos of the behaviour follow.

3/12/2017.

25/01/2018

25/01/2018. This individual stayed pecking the end of this branch for quite a while.

16/11/2016

UPDATE 11/1/20
I found out a chorusing Goldfinch flock in a local park today. Several of them were feeding on branches in two lime trees. I managed a couple of videos showing how they target areas at the end of broken branches and deftly peel bark and wood, discarding bits. If they are feeding on the bark or wood itself or on some invertebrates living in it is unclear.

Goldfinch Chorus

This morning, while I walked around the park I heard a distant loud cheerful chatter. As I approached I realised there was a flock of Goldfinches up a large horse chestnut and many of them were singing. It is the second time this week that I witness this behaviour, the first time it also happened in the morning, the flock of Goldfinches singing together from a bare sycamore. Some seemed to amuse themselves pecking the branches, but in general they were just calling and singing. Goldfinches are very social birds, they often nest in loose colonies, and, although individuals might squabble for a particular food source, they often feed together in flocks. Whereas in the summer they like the seeds of teasels, thistles and other herbaceous plants (even lavender seeds!), in the winter, they can often be seen feeding on trees, like Alder, Plane, Ash and Birch. I haven't managed to find much information about chorus singing in Goldfinches, but the behaviour has been described in the closely related American Goldfinch and Siskin, where the males in the flock joining in chorus song in winter and spring.

Goldfinch flock singing (two bulkier Greenfinches are amongst them)

Problem solving Goldfinches

I realised only recently that Goldfinch manipulation abilities are superb. They hold large seeds with one foot while manoeuvring them into position to feed, or fold stems back to hold berries or seeds securely, or hand upside down to reach the thinnest branches. Yesterday I watched a small flock feeding on the catkins of a silver birch. The closest bird to me held a catkin while feeding from it and even changed the foot it used to hold it.
 It happens that Goldfinch manipulation abilities have been known for a long time (Plinius and Gesner mention it). Golfinches used to feature in animal shows, as seen in this old British Pathe film demonstrating the string pulling ability of a Goldfinch. The bird alternatively pulls and holds a string to reach a container with water or food.

String pulling is a common experimental setup to investigate the problem solving ability in birds. Parrots, corvids parids and finches can pass the test. In a series of experiments on captive-reared Goldfinches and Siskins, Uta Seibt and Wolfgang Wickler set to explore the problem-solving abilities of individual birds and what factors influence success. The birds were reared in cages with no access to material with which they could experiment their manipulative abilities and were tested when less than 5 months old using a 7-cm string holding a thimble with food at the end.

The researchers found that there were three groups of bird. 'Inventors' (23% of goldfinches and 62% of siskins) solved the string-pulling test by themselves, some times in the first experimental session, whereas ‘imitators’ (25% of goldfinches; 10% of siskins) were successful after watching conspecifics solving the problem. The remaining birds failed the test even when exposed to an experimented model.
 Something the experiment highlighted was the remarkable behavioural plasticity of Goldfinches and Siskins as shown by the diverse repertoire of behaviours the birds used to solve the problem (getting the food in the thimble):

Several individuals of both species hovered in flight near the thimble. They never succeeded in taking food, but still tried to reach food this way when they were already able to eat via string pulling and holding. A few goldfinches and siskins stretched from the cage fence towards the thimble but without successfully touching it. Two siskins and one goldfinch reached the thimble while hanging down from the perch head down like bats. Several siskins climbed down the string and ate from the thimble. Three other siskins shed some food from the thimble by heavily shaking the string and pecked the grain from the floor. (Goldfinches never moved to the cage floor.) Eight goldfinches and seven siskins invented a special method to flick the string around the perch, thus lifting the thimble indirectly. Some individuals used several of these techniques.

In addition, some individuals showed a preference for one or the other foot to hold the string.
Additional experiments tested the effect of being reared with access to branchlets. These seemed to facilitate success, but they were not necessary in several individuals. Similarly, the presence of a model facilitates success for a large proportion of the birds (the 'imitators'). Finally, the presence of food in the thimble was also necessary for the goldfinches to lift the string.
Bird species which instinctively used their feet to clamp food or branches while foraging - like the Goldfinch - should be able to solve the test, but the experiments show that birds still vary in their predisposition to experiment with the string and in their success. What proportion of wild Goldfinches use foot-bill coordination when foraging is hard to assess, but one would expect that given that natural conditions this would be higher than in the experiments. The wild birds are exposed to a much richer rearing environment, as they have very diverse diets and have to extract seeds from an array of plants from small perennials with soft pliable stems to trees with variably flexible branchlets (dandelion, teasel, lavender birch, ash, alder, rowan to give some examples). In addition, Goldfinches are highly social birds that feed together in flocks, so the learning opportunities would be plentiful.

Goldfinch holding birch catkin with left foot. Note that the catkin is still attached to the branch and the foot helps immobilise it, facilitating food retrieval.

More information
Seibt, U., & Wickler, W. (2006). Individuality in Problem Solving: String Pulling in Two Carduelis Species (Aves: Passeriformes) Ethology, 112 (5), 493-502 DOI: 10.1111/j.1439-0310.2005.01172.x . Here.

Swinging goldfinch

A trio of goldfinches came to the feeders today. One of them, while it waited on nearby branch to feed, carried out a curious 'dance', repeatedly swinging its body from one side to the other while it called. I looked into this and found out the dance it's got a name: 'pivoting display'. In a courtship context, the display is carried out by the male and he swivels towards and away the female as he swings. The wings are somewhat lowered - which makes the golden bars more visible - and the tail spread, showing the white patches. Female also pivots, and when both sexes carry out the display it may end in copulation.
 The pivoting display is also used in aggressive contexts, and maybe the goldfinch was becoming impatient waiting by the feeder. I shall keep an eye on my visiting goldfinches and see if I can record this behaviour. I found a little video showing the behaviour in a charm of goldfinches. Check the individual at the bottom of the image from s 36.



And a great video of a pair of captive goldfinches courting.

Goldfinches feeding on ash keys

I had never seen any Ash seed predators, until today I spied a charm of Goldfinches atop a weeping ash tree in the park. The Goldfinches were sitting on bunches of keys chomping away at them. I was so surprised I checked sure they were eating the seeds and not the buds or just loitering on the tree. But, yes, they were manipulating the seeds with their bill (bottom photo). I could only find a photo of goldfinches feeding on ash keys (here). The coat of the ash seeds seems quite tough and leathery so that shows how versatile goldfinch bills are, not only extracting tiny seeds like teasel, birch or alder from their pods, but also dealing with these.

UPDATE 18/01/2014
I watched another flock in a different Ash tree today. I photographed an individual using its foot to hold the whole seed while it pecked it with its bill. Photos follow.

Charming seed predators

 I find fascinating that when you seen something for the first time, then the chances are that you would see it again, seeing helps you see more. In the last couple of weeks a charm of goldfinches have been regular visitors in the garden feeders, gorging themselves on nyjer and sunflower seeds. I was watching the goldfinches and taking photos from inside of the house, when I noticed that one of the birds that couldn't get to the feeders was feeding on rowanberry seeds (above), discarding the pulp. This is typical of seed feeding birds like finches. Finches are seed predators, unlike thrushes, that eat the berries whole, passing the seed undigested and undamaged, in their droppings, and dispersing the seed away from the tree in the process.
 There was no mention of Goldfinches in the authoritative 'Birds and Berries' by Snow and Snow. I found a wonderful, if lone, photo on Flickr here and a line in a novel that suggested that this behaviour had been noticed before:

They went down the track through a wood where a flock of goldfinches was feeding on the rowanberries [...]

Tessa Hadley, Accidents in the home, 2002

Today on a walk in the park, I noticed a rowan on a garden and had a look. A charm of goldfinches looked busy on it. I wouldn't have normally had a closer look, but I did. They were feeding on the berries, hanging from the bunches like tits, not one, not two, but the whole flock seemed to be enjoying the berry seeds. The photos from today (below) are atrocious, as it was late and the light very poor, but a record nonetheless. After a while, something spooked the birds, a Sparrowhawk perhaps, and the Goldfinches went quiet and took to the air with a group of starlings and feral pigeons. I glimpsed what I think was a woodcock before if flew behind a roof, powerful wings and long bill, but just for a second. A Blackbird called: 'seee!' from a bush, their air predator alarm call.
 Indeed, a range of finches - including Goldfinches - are reported to feed on rowan seeds occasionally: Greenfinch, Crossbill, Brambling, Chaffinch, Hawfinch, Goldfinch, Redpoll and Siskin. Indeed, for some finches, particularly Bullfinch and Pine Grosbeak rowan seed in autumn can be their staple food. But rowan is a masting tree, where crop is very variable across years, with bumper crop, the 'masting years' interspeded with poor or failed crops in some. In the winter of 2004-2005, simultaneous irruptions of boreal Waxwing, Pine Grosbeak and northern Bullfinch occurred, all three birds liking rowan berries. Bullfinch local movements and irruptions in western and southern Europe have been linked to the strength of rowanberry fruiting crop.

This goldfinch appeared to use her foot to hold the berry in place

  A couple of weeks ago I spotted a juvenile Common Rosefinch, a rare visitor to these shores, feeding on rowan berries

Juvenile Common Rosefinch feeding on Rowan berries. 4/11/2013.

Some finches might use rowan depending on local availability. As this year rowan berries are plentiful and the thrushes have barely made a dent on the crop, Goldfinches and other birds may take advantage of this resource opportunistically.

References
Pennington, Mike G., and Eric R. Meek. (2006). The ‘Northern Bullfinch’ invasion of autumn 2004. British Birds 99: 2-24.

Munilla, I., and Guitián, J. (2012). Numerical response of Bullfinches Pyrrhula pyrrhula to winter seed abundance. Ornis Fennica, 89(3), 197-205.

Fox, A. D., Kobro, S., Lehikoinen, A., Lyngs, P., and Väisänen, R. A. (2009). Northern Bullfinch Pyrrhula p. pyrrhula irruptive behaviour linked to rowanberry Sorbus aucuparia abundance. Ornis Fennica, 86, 51-60.

Snow, B. K., and Snow, D. (2011). Birds and berries. A&C Black.

Raspe, O., Findlay, C., and Jacquemart, A. L. (2000). Sorbus aucuparia Journal of Ecology, 88 (5), 910-930 DOI: 0.1046/j.1365-2745.2000.00502.x

Goldfinches pecking for grit

I found this flock of Goldfinches pecking the mortar between bricks to get grit. Most bird species that feed on plant materials contain grit in their gizzards. Seed-feeding birds aid digestion by incorporating insoluble grit (silica) into their diets, so that itscours the seed shell and exposed the nutritive inside to digestive enzymes or just helps with grinding the seeds. Soluble grit, containing calcium carbonate (limestone or grit of organic origin) is also actively sought for in preparation for egg laying, as it is a component of egg shells. I guess the mortar has the right type/size of grit for goldfinches, as I have found several photos showing similar behaviour (see here and here). As mortar contains both soluble (lime) and unsoluble (sand) grit, it is unclear which one the goldfinches are obtaining from it.

Planes and goldfinches

This morning coming into work I heard the unmistakable chirps of squabbling goldfinches. There was a large flock feeding on a line of plane trees. While I climbed the stairs I thought delightedly that the window in our lab overlooks the trees, so I could have a level view of the feeding goldfinches. There they were, hanging from the bauble-like seed balls or balancing from the thin stems holding them. London plane trees (Platanus x acerifolia) is an important food resource for goldfinches, as it provides seeds during the autumn months into the winter. The photos didn't come brilliant - I blame the dirty windows - but I think the one on top captures the atmosphere of the feeding flock. I count seven, how many can you see?

More information

Sachslehner, L. M. (1998): The significance of Plane-trees Platanus x hispanica M. as a food resource for Goldfinches Carduelis carduelis L. in Vienna. Egretta 41: 90-101.

Goldfinches and dandelions

You don't need to get out much to enjoy wildlife. Literally, sometimes surprising things happen right at your doorstep. This morning I had to stop short of opening my front door as I realised a pair of goldfinches were standing next to it. One of them was grabbing a couple of dandelion heads - that had probably tumbled over with its weight - and feeding on the unripe seeds. This went on for quite a while. The photographs were taken through glass.

Goldfinches are specialist on small seeds, they benefit greatly from flocking when foraging as they need a lot of effort to obtain enough biomass from tiny seeds that have to be prepared and swallowed one by one and they can devote less time to scanning for predators when they are in a flock.

Gluck investigated these effects on Goldfinches feeding in orchards in Germany during the breeding season. He recorded Goldfinches feeding on milky ripe seeds from 20 plant species. Of these, most of his observations were on five species: Dactylis glomerata (Gramineae), Knautia arvensis (Dipsacaeeae), Senecio vulgaris, Taraxacum officinale and Tragopogon

pratensis (Compositae). The following graph illustrates the relationship between the number of dandelion seeds ingested per minute and flock size in Goldfinches, showing that even in small flocks of 5 birds each bird can almost double their seed intake per minute.

I am a big fan of dandelions and today's sighting is going to make me do even less weeding around the garden.

More information

Erich Glück (1986) Flock size and habitat-dependent food and energy intake of foraging Goldfinches. Oecologia, 71:149-155.