Pecking Order – the hierarchy at the feeders

Bird feeders act as central congregation points for local birds, but when they start panic buying, which species is top of the pecking order?

A study carried out by the University of Exeter and the BTO suggests that heavier birds are more dominant at bird feeders, allowing species such as House Sparrows to gain superior access to higher “value” food that is either high in energy or efficient to consume (e.g sunflower hearts require less energy to eat than a sunflower seed with the husk still on).

Goldfinches tucking into sunflower hearts - a high "value" food

This idea of dominance was calculated by recording which of two feeders a bird visited (either a “low value” sunflower seed with husk feeder or a “high value” sunflower heart feeder), the length of time a bird spent on the feeder, how many pecks a bird made whilst at the feeder and the outcome of any interactions between birds of different species (i.e. would a House Sparrow displace a Blue Tit from a feeder?) 

The ten species involved in the study, ranked by dominance were as follows: House Sparrow, Greenfinch, Nuthatch, Robin, Goldfinch, Great Tit, Dunnock, Chaffinch, Blue Tit and Coal Tit.

A Robin eyeing up a feeder

Whilst there was a clear link between the average mass of the species and their dominance rank, Chaffinches were somewhat less dominant than expected, given their mass. This was an interesting observation because there was no link between families of birds and their dominance (e.g. there was no evidence to show that Finches (Fringillidae) were more dominant that Tits (Paridae) and their dominance wasn’t influenced by their evolutionary histories), perhaps suggesting as a reminder that normal foraging behaviour might influence dominance at a feeder. After all, Chaffinches are normally ground-feeding birds and many of us will have seen territorial Robins fighting off other species in our gardens. 

The dominant species, out of those studied, was House Sparrow

However, whilst the three Tit species involved in the study are similar arboreal foragers, the Great Tit was considerably more dominant than the Coal or Blue Tit due to its increased size.

We can also see how bird feeders have influenced the behaviour of our garden birds; birds that are less dominant adjust their feeding activity in order to maximise the amount of food they can access. Because these smaller, less dominant birds spend less time at a feeder, the rate at which they peck is much higher than the larger, dominant birds that spend more time at the feeder. This way, it means that feeder still provide a potentially life-saving food source for garden birds.  

The authors of the study mention how it would be interesting to see if this pattern of heavier bird = more dominant extends to individuals within a species, rather than just between species. However, you’d need a way to tell individual birds apart and would need to weigh them regularly, something that could only realistically be achieved with a captive population.

The full article is freely available here, with graphs and statistical analyses: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0202152#sec007

The opening phrase of this blog does highlight a problem with bird feeders though: their ability to spread disease. Germany has seen an outbreak of Suttonella ornithocola which has led to startling numbers of deaths in Blue Tits, thanks to their affinity for feeders. Whilst the disease is yet to take hold in the UK, it should serve as a reminder of the importance of keeping feeders clean.