Herring Gull
Life for the chicks of these noisy birds – as commonplace on warm days at the seaside as fish and chips and ice-cream – is nothing short of fascinating
Dominic Couzens on the seaside species with an interesting story!
It is high summer, and at nests throughout Britain, adults are bringing food offerings to their dependent young. Whatever the species involved, it is a delightful and compelling scene, redolent of the strong reliance that a young bird, be it a helpless, naked nestling or a scuttling fluffy chick, has upon the efforts of its parent or parents. Think about the sheer begging madness of a brood of fledged Blue Tits and their exhausted parents coming and going, plumage all out of place, libido a piece of history. The contract between adult and young would, you might think, be unbreakable. What is more important to an adult than the welfare of its chicks? What greater expression of its success and productivity could there be than a clutch released into the wild, fledged and ready? Those endless feeding visits, which are a product of an adult’s health, foraging ability, energy levels and – yes, personality – are the unique package an individual bird offers its own species. The moments of preparation – territorial defence, pairing up, guarding the mate, building the nest – all boil down to this. What, then, can one make of a set of observations made within the fevered world of the Herring Gull colony, where in some cases the contract is apparently turned on its head? Occurring at consistent frequencies is a phenomenon known as ‘chick-generated brood parasitism’. Another way of putting it is that, hard to believe though it may be, the chicks fire their parents. They evidently size up their situation and decide that the grass really is greener on the other side of the territorial divide. They skip over the imaginary fence and try to get adopted by the parents next door or nearby; birds whom they hope will do a better job of feeding them. Think about this for a minute. These are chicks whose life can be counted in days. Their parents will be at least three
The adults can recognise their own chicks, so adoption is something of a mystery
years old, and probably more. Yet the ingenues overrule their elders and providers. Presumably, something deep inside makes them react to the onset of starvation. It is a formidable leap of desperation, truly extraordinary in the first days of life. What makes this abandonment of blood parents more remarkable still is that the atmosphere in a Herring Gull colony could never exactly be described as friendly. Relationships between adults and strange chicks aren’t even neutral; they are often hostile. Chicks that are left alone on territories are often randomly attacked by neighbours, and frequently killed. Some Herring Gull adults will eat a lost chick and, in another scarcely believable strand of behaviour, a few adults actually specialise in cannibalism. The sinister truth is that in many colonies, a very small proportion of adult males are like this, flying back and forth around the nests and eating chicks as their main diet. Life for small chicks is perilous even before you take into account such neutral predators as Peregrines, Foxes or, in places the Herring Gull’s nemesis, the Great Black-backed Gull.
Dangerous gamble
And yet, under these unpromising conditions, some chicks scuttle away from the natal umbrella to seek some chance of life next door, or down the street. Neglected and malnourished, they are refugees in their own colony, throwing themselves upon the vagaries of potential adopters’ individual moods and tendencies. It is a dangerous gamble, and about a third of broods seeking adoption are killed by adult gulls. It does sometimes work, however, and another third of waifs and strays are accepted by a new family. The novel chicks play a good diplomatic role, performing appeasement postures not just with their new parents, but with their step-siblings, too. In successful adoptions, the new chicks tend to be older and larger than the incumbent brood. Nobody is quite sure why any adults undertake the responsibility of a new brood, bearing in mind that it compels them to protect and nourish unrelated chicks. In many cases the parents bring less food to the new additions, which continue to be underfed, begging the question as to why either party bothers. The adults can recognise their own chicks, so adoption is something of a mystery. Amazingly, there are records of young Herring Gulls being adopted by pairs of Great Black-backed Gulls, so something dulls their normally violent bent. The strange case of chick-generated brood parasitism is not the only curiosity in the parent-child relationship in Herring Gull colonies. There is also an unequal relationship within the brood itself. Gulls are unusual among birds in typically laying three eggs to the clutch. The second egg is normally laid a day after the first, but the third egg arrives two days later still, sometimes more. The adults begin incubation with the first ‘A-egg’, but their brood patches aren’t fully formed until the B-egg comes along, when it sets forth in earnest. The female lays the C-egg some time later, meaning that the C-chick is invariably smaller and lighter than its older siblings. This gives rise to a potential inter-brood conflict. Some studies have found that the C-chick suffers in competition with its older siblings, losing weight and suffering more from predation. Other studies suggest that it is fed properly. Either way, some C-chicks are known to go down the adoption route,