Springwatch Unsprung: Why Do Robins Have Red Breasts?. Jo Stevens

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      Adults are more aggressive towards larger chicks that may outcompete their smaller siblings and monopolise feeds. Unsurprisingly, after being attacked a chick stays out of its parents’ way and stops begging to be fed for a while. This allows the smaller chicks a chance to receive their fair share of food. So the parent may be trying to ensure all chicks are fed equally and also force the bigger chicks to fend for themselves, encouraging them to become independent.

      Despite the squabbles, moorhens have very attentive families. Moorhens and long-tailed tits are the only British birds to breed cooperatively; that is, youngsters from the first brood sometimes stick around to help raise the second brood. This gives the juveniles valuable experience in bringing up chicks and helps their siblings to survive. As is so often the case in human families, the older moorhen brothers and sisters support their frazzled parents to keep the peace.

      Family Affair

      Do fox families contain youngsters from different years in the same den? If so, do the older cubs play any part in rearing their younger siblings? Alan

      Foxes are usually seen alone but they don’t lead solitary lives. Most fox families consist of an adult male and female plus their cubs. When the cubs are born they are just 10–14 centimetres long, blind and helpless. They’re completely dependent on their mother for milk and warmth as they cannot regulate their own temperature. She will stay with them around the clock for the first couple of weeks. During this time, the male will bring her food but sometimes the family will be assisted by other adult helpers too, usually vixens. These helpers often don’t breed, and when the mother returns to hunting duties they will also help to look after the cubs – groom them, play with them and bring food to the den.

      These helpers are often daughters from previous years, but they could also be the main vixen’s sisters or even her mother once she has passed breeding age. About one in three fox families has one or more non-breeding vixen helping out, and there’s usually a hierarchy so that only the alpha female gives birth. Studies have shown that helpers don’t necessarily increase the cubs’ chances of survival but they do take the pressure off the parents, which don’t have to work so hard to feed the cubs.

      So what’s in it for the helpers, when they could be raising cubs of their own? It may be a case of ‘kin selection’, a strategy that means sometimes it’s better to help raise a relative’s young even at a cost to the individual. When the time comes for a fully-grown cub to disperse, it has to weigh up the costs and benefits of staying against the risks of leaving home. If it stays, the cub may not breed for a year or two but it might inherit the territory. By leaving home the cub may have young of its own by next spring but it must find its own territory first. Mortality can be high for dispersing cubs so it is a difficult choice for them to make.

      Choosing to stay at home doesn’t always mean that a fox won’t get the chance to breed, though. In 2012, Springwatch followed a fox family that had a mammoth litter of eleven cubs living under a garden shed in Potter’s Bar. Most litters only have four to six cubs so this was unusual. After watching the family closely for several weeks it became apparent that there were actually two adult females, one dominant and one subordinate, and both appeared to suckle the young. It seems that both vixens were mothers and they had pooled their litters to raise them cooperatively.

      Dogged by a Bad Smell

      Just a quickie, why do dogs love to roll around in fox poo? What is the attraction? Jackie

      Members of the canine family, such as wolves, dogs and foxes, have a very acute sense of smell. Humans are primarily visual creatures while a canine’s world is ruled by scent. Dogs and their wild relatives can pick out the faintest scents using their wet noses and millions of olfactory receptors. A large proportion of a dog’s brain is devoted to processing all this olfactory information and their sense of smell may be several million times more sensitive than ours. In the wild they would use this skill to track down prey or other members of their species, but we humans have exploited the dog’s nose for a wide variety of tasks, from finding truffles and recovering shot game birds to detecting explosives, illegal drugs and missing people.

      Scent is vital in fox communication too. Foxes often mark their territory by defecating in conspicuous places, such as on top of molehills, at the junction of paths or on tussocks of grass. It’s thought that a fox’s faeces provides clues to the animal’s sex, fertility, health and status. Both fox urine and faeces have a distinctive, musky smell that even our weak human noses can easily detect!

      Why then, if dogs have such a sensitive nose, would they choose to roll in something as stinky as fox poo? It’s thought to be a relic of their wolf ancestors and may have several purposes. Wolves roll in something pungent like a rotting carcass or another species’ droppings as a form of olfactory camouflage. They first rub their cheek against the object then slide against it, covering themselves in a foreign scent. This may disguise the wolf’s own smell so that it isn’t detected by prey when attempting to hunt. Scent rolling may also enable a wolf to bring back any novel scent it finds and share it with the rest of the pack. When the wolf returns it is sniffed and licked by other wolves that then pick up the scent. Another theory is that certain scents may act like perfume or aftershave and make the wolf more attractive to others.

      Regardless of the motive, dogs that have rolled in fox poo certainly aren’t more attractive to humans! Not only is the smell offensive, it’s also unhygienic. Fox droppings may carry diseases and parasites like tapeworms and roundworms, so it goes without saying that if you wash the fox poo off your dog make sure you wash your hands very thoroughly afterwards.

      The Sweet Smell of Success

      Do starlings like scented nests? Earlier this spring I saw a couple of starlings pulling bits out of my lavender bush and flying off with them, at about the time that they were nesting. I can only assume they like the smell. By the way, I now have approximately 50 starlings – adults and young – feeding in my small town garden. Sue

      Male starlings have been known to adorn their nest with yarrow, parsley and hawthorn as well as lavender. They might be attempting to court a female by saying it with flowers but it seems that scent is more important than beauty. Several species of birds appear to have a penchant for aromatherapy, not just starlings, and they continue to bring scented plants to the nest once their chicks have hatched.

      On Springwatch, cameras inside a blue tit nest showed the adults bringing in mint – they didn’t feed it to the chicks but placed it around the nest. At first, biologists thought birds might be using aromatic plants to deter parasites such as lice, maggots and ticks, much like we use mothballs. In fact, French biologists have discovered that plants such as mint, lavender and the curry plant are used for their antibacterial properties. Blue tit chicks raised in nests lined with these aromatic plants have fewer bacteria on their skin. This may allow them to put effort into their growth rather than strengthening their immune system. Chicks surrounded by scented leaves appear to grow more quickly and thus have a better chance of survival. Individual blue tits have particular preferences for which plant they collect – some prefer mint while others always collect lavender, even when both herbs are available.

      A similar study on starlings showed that the air inside nests lined with fresh herbs is full of volatile compounds – smelly chemicals from the plants’ essential oils. They include limonene (citrus-like), myrcene (from thyme) and phellandrene СКАЧАТЬ