Dear Readers, I have just acquired (yet another) new book. This one is ‘Garden Birds’ by Mike Toms, and it’s in the much beloved New Naturalist series. So, I thought I would share some of its wisdom with you, in the form of a single fact about some of my favourite garden birds.
Unlike most birds, Jackdaws start to incubate their eggs part-way through the laying process rather than when all the eggs have been laid, which leads to chicks of different sizes being in the nest at the same time. The oldest, largest chicks are most likely to be fed, so in times of shortage, the youngest chicks will probably die (though when pickings are good all will probably survive). When there isn’t much food about, the male chicks (who are larger than the females) are most likely to die because they require more calories. Broods produced at the end of the season when conditions were poor were also more likely to have more female chicks both hatched and reared.
It seems to be the case in many species that when times are hard, nature favours females.
A major food for starlings during the breeding season is the larvae of craneflies (leatherjackets) – I often see the birds marching across Muswell Hill Playing Fields, probing about for these tasty morsels. Changes in agricultural management, largely due to the use of sheep rather than cattle for grazing, and the draining of meadows and wetlands where adult craneflies used to congregate, are thought to be responsible in part for the decline in numbers of starlings by 89% between 1967 and 2015. An additional pressure has been changes in building regulations, and the movement towards plastic rather than wooden barge boards (the boards used on the gable end of a house), which means that new houses are significantly less friendly to nesting birds than old ones.
Goldfinches in the wild feed on the seeds of plants such as thistle and teasel, and while they might at first have been attracted to gardens by the provision of nyjer seeds, there seems to be a pattern emerging whereby they prefer sunflower seeds to nyjer when both are offered. This is certainly something that I’ve noticed in my garden, and I’d love to know if you’ve seen something similar! In the wild, goldfinches apparently prefer seeds that are still under-ripe and ‘milky’.
Robins are prone to nesting very low down in a shrub, and sometimes even nest on the ground. This makes them one of the three most vulnerable garden species to cat predation (the other two are the house sparrow and the dunnock). However, they are very wary around their nests: they have been seen to drop the food that they are carrying for nestlings if they think they are being watched, and may even make a visit to a ‘false site’ to confound the observer. This seems to me to show that robins have a ‘theory of mind’ – they have a sense of what the watcher might be thinking (i.e. that they want to know where the nest is) and act accordingly to protect it.
The first pair of collared doves bred in the UK in 1955. Today, there are 990,000 breeding pairs. This remarkable expansion has been powered, in part, by the collared dove’s ability to breed year round: a pair can squeeze as many as five breeding attempts into a single year. Each nest holds only two chicks, but these are much more likely to survive than a larger brood. The species is also making headway in North America, where 50 birds escaped from a bird breeder in the Bahamas. Some soon turned up in Florida, and they are currently advancing north and west.
In house sparrows, the dominance of a male within the colony is indicated by the size of the black ‘bib’ under his throat. More dominant males not only do proportionately more of the work of nest-building, provisioning and incubation than small-bibbed males, they also do more in the way of defending the nest from predators, probably another good reason that females tend to choose more dominant males as partners. A higher proportion of the nestlings in the nests of large-bibbed males fledge, too.
And a second fact that I cheekily wanted to sneak in: sparrows make a ‘chirrup’ call when they find a food source that is large enough to be shared, but stay silent when there’s only enough for them. Very sensible!
Although you might think that you’re seeing the same couple of blue tits on your bird feeders, studies on ringed birds have shown that you might in fact be seeing up to a hundred different individuals – blue tits in the region will make a ‘tour’ of the local gardens, dropping in for a quick bite at each one. This really shows up the importance of the continuity of habitats – blue tits are reluctant to cross busy roads or other unsuitable habitat, but will happily make a short hop from tree to tree.
In a few weeks’ time, there will be a sudden drop in the bird activity in the garden. Many species will be moulting and taking a hard-earned rest after the breeding season, but some blackbirds take off on holiday – many will move into the countryside to feast on berries. However, some just seem to fancy a change of scene: one ringed blackbird bred in a garden in Norfolk but spent her winters in a Devon garden every year, probably to escape the wind that blows in straight from the Steppes.
Incidentally (says she, sneaking in yet another second fact) blackbirds will eat tadpoles, pulling them out of the pond and bashing them on the ground. The birds will also be struggling to find enough earthworms to eat at the moment, as the soil is so dry and the worms will be keeping a very low profile. You might want to do some watering (or watch after rain) and see what happens.
So, that’s just a few garden birds. What a great book! The New Naturalists never let me down. I am waiting with great anticipation for one on ‘Ponds and Puddles’ that is promised for 2022. I think I will have to keep working until I’m eighty simply to fund my book buying.