A blog post by Phil Sheldrake on 30 March
So, we have four eggs! A full clutch? Well quite possibly although peregrines do sometimes lay five, or more rarely six eggs. I hope four is our full clutch, not least for a bit of normality but in the interests of our falcon herself. You might recall Sally, of BBC Springwatch fame in 2017, laid five eggs which she had difficulty incubating, an egg frequently being left uncovered. Only one of this clutch hatched, Sally however, went on to display amazing qualities as a mother, not only rearing this chick to fledge successfully but also the introduced chick she adopted as a surrogate.
Whilst incubating a five-egg clutch might be difficult for our falcon (female), it would present a real challenge for the male, known as the tiercel. As with most birds of prey (or ‘raptors’), the male is smaller than the female; ‘tiercel’ comes from the Latin word tertius meaning ‘one-third’, the male being typically one-third smaller than the female. This is known as sexual dimorphism – why is the female larger than the male? Well, there are any number of explanations, however, one would be the need for females to store greater reserves during the breeding cycle when she will invariably be hunting less. If you’re interested, there are a few plausible theories in this bitesize link: https://web.stanford.edu/group/stanfordbirds/text/essays/Size_and_Sex.html
Both falcon and tiercel will incubate the eggs although the falcon will do most, the tiercel doing the lion’s share of the hunting during this period. Full Incubation will begin with either the penultimate or last egg and last around a month and possibly up to 35 days….I notice our falcon has been sitting pretty tight the last few days….May Day chicks??
Phil Sheldrake is the Cathedral’s Nature Conservation Adviser. He describes himself as a social conservationist, focused on bringing people and the natural world closer together. Phil began life as a teacher, but 25 years ago a lifelong love of wildlife signaled a career change and he swapped the classroom for the great outdoors. Starting his RSPB career as a reserves warden in Wales, he went on to manage the Wessex Stone-curlew Recovery Project and most recently covered Wiltshire & Gloucestershire d as Conservation Officer. He is a founder member of the (Eurasian) Curlew Forum, a national network for curlew conservation groups across England. Phil first approached the Cathedral in 2011 with the idea to provide a nest box for the peregrines he had seen roosting on the Tower over winter. In 2014 his efforts were rewarded with peregrines returning to nest successfully after an absence of 61 years. Since then Phil has continued to support the Cathedral in development of the peregrine project including the provision of the webcam to give us a window into the life of this charismatic bird. Phil works closely with another peregrine expert, Granville Pictor of the Wiltshire Ornithological Society and Cathedral Clerk of Works, Gary Price. He also co-ordinates the peregrine ringing, with the help of naturalist Ed Drewitt of the British Trust for Ornithology.