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

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      City birds have adapted to their surroundings by using cigarette butts instead of plants to scent their nests. Research in Mexico showed that by lining their nests with the nicotine-infused filters from smoked cigarettes, house sparrows and finches reduced the number of mites and other parasites. Nicotine is a natural insect repellent produced by the tobacco plant as a defence against herbivores, so it’s not a surprise that it deters parasites too. Over the years, Springwatch has received many photos of blue tits and other birds nesting in cigarette butt bins, so it seems that British birds have learned the same trick.

      Hungry Herons

      We recently saw a heron catch a wounded bird. It decapitated it then took it to the water’s edge and ate it. I thought they were fish eaters, or will they eat other things if it’s an easy catch? Lesley

      How common is it for herons to ‘nick’ moorhen chicks? This weekend I saw a heron bully two adult moorhens until they moved from the nest and it then nicked a chick and flew off! Tessie B

      Herons aren’t fussy eaters and have a very varied diet which includes small mammals, insects, little birds and amphibians as well as fish. They will catch birds up to the size of a water rail, so moorhen chicks are just a small snack.

      Despite their long neck, herons have the same number of vertebrae as other birds but the bones are specially configured so that herons can bend their neck into an ‘S’ shape, allowing them to strike quickly. Usually, herons rely on stealth for hunting, waiting motionless before launching their long, sharp beak to snatch a fish or other prey. This technique is imaginatively known as ‘standing still’. Another technique is ‘walking slowly’, during which, yes, you’ve guessed it, they walk at a very slow pace to prevent spooking their prey. However, herons are large birds, standing about a metre high with a two-metre wingspan, so they’re not afraid to use brute force and bullying to get a meal if necessary, especially when they have hungry chicks to feed.

      The type of food a heron chooses depends on the time of year and what is locally abundant in that season. Pellets collected from breeding colonies provide clues to which prey the adults are catching. Heron chicks are reliant on their parents for a long time, spending about 50 days in the nest, and they may not be independent until they are 80 days old. Herons are very adaptable hunters and can react to changes in prey availability, so the food brought to the chicks may change over the weeks. When there are plenty of small ducklings in May and early June, these can make up a large part of their diet. Some colonies feed mostly on small mammals such as water voles, mice, rats and even young rabbits. Although they are usually seen hunting in or near ponds and rivers, during the winter herons may hunt away from water, looking for small mammals in fields and pastures.

      Herons will also make the most of a well-stocked garden pond if they find one, so if you want to hang on to your fish, try covering the pond with a fine mesh net and provide hiding places for the fish by planting waterlilies and other aquatic plants. You can also make it more difficult for herons to get to the water’s edge by encircling the pond with a barrier of taut strings or wires 20 centimetres and 35 centimetres above the water level. Herons are pretty bright birds so plastic decoy herons don’t appear to be much of a deterrent and may even attract a heron to hunt.

      Purrfect

      Do wildcats sound the same as domestic cats? Do they purr? Avril

      As most cat owners know, domestic cats communicate with a variety of calls and vocalisations including hisses, growls, chatters, as well as the more familiar purring and meowing. Hissing and growling are clear signs that a cat is feeling threatened or angry. A female will ‘caterwaul’ when she is fertile – a bloodcurdling wail that advertises to local males that she is ready to mate. Kittens meow to their mothers to request food or attention and an adult pet cat continues this behaviour with its human owner. Those plaintive cries asking to be fed, let inside from the rain or demanding to be stroked are hard to ignore! Whatever delusions of grandeur your moggy may have, only a few large cats such as lions, tigers and leopards can roar.

      It’s very difficult to determine exactly when cats became domesticated because the skeletons of domestic cats and their wild predecessors are so similar. However, the skeleton of a domestic cat was found with its owner at an archeological site in Cyprus, having been buried about 9,500 years ago, so domestication must have occurred before then. Genetic studies suggest that cats began living with humans when agriculture blossomed in the Fertile Crescent of the Middle East around 12,000 years ago. Wildcats were probably attracted by the rodent pests that were drawn to our ancestors’ grain stores and stayed to take advantage of this food source. No doubt, humans would have welcomed these cats if they helped to keep pests at bay. The origins of our pet cats are a bit murky but biologists suspect that their ancestors include the African and European wildcats, both subspecies of Felis sylvestris that might have interbred in the Middle East region.

      Wildcats are found across Europe but in the UK they are restricted to Scotland where they are considered to be a unique subspecies, Felis silvestris grampia. They are superficially quite similar to our domestic cats and can interbreed with them, but their behaviour is quite different to that of a pet tabby that will sit on your knee. They are truly wild creatures and very elusive in their natural habitat.

      Scottish wildcats lead a solitary life most of the time so, although they can make the same vocalisations as domestic cats, they generally remain silent. Instead they communicate by scent, marking their territories with faeces, urine or their scent glands. They only become vocal when they meet another cat during the breeding season or when they have kittens.

      Most species of cat, large and small, can purr. Exactly how cats produce the purring sound is not yet understood entirely, but it is thought that the glottis (the area of the larynx with the vocal cords) is rapidly expanded and contracted as the cat breathes in and out, creating the characteristic vibration sounds. (We contract our glottis to create an ‘h’ sound in speech.) Unlike domestic cats, adult wildcats do not purr. Kittens purr from birth, especially when they are suckling, and purring is often interpreted to mean that the cat is content or happy. However, adult domestic cats sometimes purr during stressful situations or when they are in pain, perhaps as a means to comfort themselves or encourage others to provide care. Cats have learned that purring is a virtuous cycle – by showing pleasure they receive more pleasure, whether they are manipulating their mother or a cat-loving human.

      Eggstatic

      How can a tiny bird lay three or four eggs that have a total volume similar to that of themselves? Lin

      Which bird lays the most eggs in one go? Dicky

      Producing eggs requires a lot of effort and energy. In robins, for example, a complete clutch may be equivalent to 90 per cent of the female’s body weight. During the laying period, female birds need to rest and eat extra calories – they often rely on their partner to bring them food. Each egg must be provided with a fat-rich yolk to feed the growing embryo, which is surrounded by egg white (albumen) and then encased in a calcium-rich shell. Not only is finding extra food and producing the eggs energetically costly but birds also have to raise their metabolic rate to generate enough warmth to incubate them.

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