The corncrake is a divisive bird; exotic rarity, or noisy pest! Whichever camp you’re in, here are a few things you always wanted to know about corncrakes but were too afraid to ask…
What’s a corncrake? a pigeon-sized, brown, migratory bird, the corncrake is famous for its repetitive song “crex-crex; crex-crex… ”. This is the male’s mating call and the female is irresistibly drawn to it. He can repeat this call up to 6 million times through the summer.
Migration Traveling the 3000 km from Africa to Europe for the summer takes them nearly two months. After breeding, the adults moult in August then head off south again in September and October. They spend nearly a third of their life in transit and many birds do not survive migration.
Heard but not seen Corncrakes like to conceal themselves in tall vegetation. This is their adaptation to avoid predators and they will run away from danger through the grass rather than fly or break cover. In April when they arrive back here, tall grass is in short supply. Instead, they find refuge in the rougher vegetation along sheltered ditches and walls until the meadow grasses begin to grow.
Speed mating Most bird species keep the same mate throughout their life but not the corncrake. Once the male has secured a female, she’ll choose one of the nest sites that he has prepared and begin to lay up to 10 eggs. By the time she has laid half the clutch however, the male moves on to woo another mate with his nocturnal singing. Alone, the female will incubate and raise the brood before she too finds another mate for her second brood.
The males may lack staying power, but equally, she is not the most attentive parent. She abandons her chicks when they are about 12 days old; leaving them, still flightless, to fend for themselves until they fully fledge after 35 days. This form of speed mating and compressed parenting is the corncrake’s adaptation to the pressure of successful breeding in the short summer season.
They don’t live long Often there are favored spots for corncrakes and it’s easy to imagine that the same bird is returning to his patch year after year. However, only 1 in 5 of the adult corncrakes present each spring make it back the following year. This means that most of the males singing in the spring of any given year were born the previous summer. And as they return to within a few kilometers of their birth site, chances are it was their dad you heard last year. Their maximum life span is still only 3 years.
This is quite an attrition rate. To maintain overall numbers, each corncrake must produce a large number of offspring. Corncrake populations can decline rapidly if they are unable to breed successfully and produce enough chicks to replace the adult birds that die.
Corncrakes love crofts Corncrakes are found on Scotland’s north-western archipelago from Shetland and Orkney down through the Hebrides, with Durness holding the only remaining mainland population. These are crofting areas where low-intensity beef cattle production still exists and this system suits the needs of a corncrake well.
Corncrake friendly Crofters do two key things to help corncrakes; they delay their mowing until August when most second broods will have hatched. And they mow the grass from the middle, working out towards the field edges, forcing the birds to safety while allowing them to remain in the long grass. Traditionally the cut would start on the field edge and work inwards, effectively corralling the birds, who would stay in the uncut grass. The final strip in the middle of the field would then get mown, along with the birds.
Recovery from extinction Corncrakes were once common all over the UK but they suffered huge declines throughout the 20th century. By the early 1990s, they were on the brink of extinction. Happily, numbers are on the increase with over 1200 birds being counted in Scotland in 2014. The corncrake’s recovery is a tribute to local crofters whose stewardship of the land has provided these birds with the habitat they need to breed successfully.
The summer survey The population on Skye is still quite fragile. The best places to hear them are on Trotternish and Waternish between May and July on warm, still evenings. You’ll easily hear them from the roadside. Keeping out of the meadows is important to avoid disturbing them or trampling the vegetation.
All information we have about where they are calling and their calling patterns helps build a picture about their breeding activity and the population in general. So if you hear any corncrakes
on the Isle of Skye, please give me a call!
RSPB Corncrake project Officer, Isle of Skye