Black Guillemot Life Cycle: Nest Building To Fledging (and everything in between)
The Black Guillemot, also known as the “Tystie” in the Scottish Isles, is a relatively small seabird. Smaller than a Guillemot and slightly larger than a Puffin, the Black Guillemot is easily recognisable during the breeding season.
Both sexes share similar markings which include; black feathers all over apart from a white patch on each wing, a black bill and red legs and feet, the inside of the mouth is also red.
During the non-breeding season, the Black Guillemot takes on a patchy black and white plumage and the legs become less deeply red coloured. They keep the white wing patches but the underparts of the body become white and the upperparts become white and black barred, the head turns white but the bill remains black.
Keep reading to find out more about these fascinating members of the Auk family.
Table of Contents
How Long Does A Black Guillemot Live?
The average lifespan of the Black Guillemot is around 11 years and they typically start breeding when they reach the age of 4 years. Given favourable conditions and ample food, the Black Guillemot can survive for more than twice the average age.
There have been individuals that have lived for as long as 24 years and 8 months according to ring data.
How Fast Can A Black Guillemot Fly?
Black Guillemots are skillful divers and can stay underwater for longer than 2 minutes when hunting for food. But that doesn’t mean that they cannot fly.
In general flight, the Black Guillemot typically reaches speeds of up to around 12.5 mph (20 km/h). However, if they are being chased or travelling over long distances they can reach speeds of up to 25 to 31 mph (40 to 50 km/h).
Are Black Guillemots Aggressive?
Although not generally considered to be aggressive, Black Guillemots can show levels of aggression especially during the breeding season. They can become intensely territorial around nesting sites, eggs and chicks.
They defend their nests by perching on stones, calling with a shrill whistle and lunging towards intruders with open bills. They can also chase intruders and take on a defensive walking stance with their backs hunched.
The first signs of aggression towards an intruder include standing or walking slowly towards them with a hunched posture, drawing in their necks, pointing their bill at the intruder and holding it open in a downward angle.
The young chicks can also display aggression to their siblings around 4 to 12 days after hatching.
What Is A Black Guillemot’s Habitat?
Unlike the majority of European Auks, the Black Guillemot is typically found in ones or twos around rocky islets. They are predominantly found in larger sea lochs of western Scotland and the northern and western isles.
They can also be found in Ireland, the Isle of Man and a few scattered sites across Wales and England.
They prefer rocky shores for nesting as well as on cliffs, under harbour walls and buildings. When the breeding season is over they are mainly found at sea although they tend to remain in waters no deeper than 164 feet (50 metres).
How Long Does It Take For A Black Guillemot To Build A Nest?
Black Guillemots typically don’t take too much time to build a nest. It can take anywhere between a few hours to 1 to 2 days depending on the circumstances.
They don’t build nests in the traditional sense, they often use natural cavities such as rocky crevices, cliff ledges, or even man-made structures like under docks or in stone walls to lay their eggs. These locations provide shelter and protection from predators.
The nest itself is quite simple, consisting mostly of minimal material like pebbles, small stones, or just the bare ground. Sometimes, they may add a few bits of vegetation or other debris to line the area, but the construction effort is generally minimal compared to many other bird species.
The time it takes for a Black Guillemot to prepare a nesting site can vary depending on the availability of a suitable location. Since they often reuse the same sites each year, the preparation time may be very short if the location is already in good condition.
Eggs
Once the nest has been completed to the satisfaction of both parents, the female will lay her eggs.
When Do Black Guillemots Lay Eggs?
Black Guillemots typically lay their eggs between late May and mid June. The exact timing for egg laying depends on climatic conditions and the temperature of the seawater close to the nesting site.
Warmer springs can cause Black Guillemots to start laying eggs earlier in the year. It has been estimated that for every 1o C increase in the surface temperature of the water in April can mean the breeding season will start 2.5 days earlier.
How Many Eggs Does A Black Guillemot Lay?
The female Black Guillemot will lay 1 to 3 eggs with a typical clutch containing 2 eggs. Once the last egg has been laid, the incubation starts.
The eggs are incubated by both parents until they hatch.
What Do Black Guillemot Eggs Look Like?
Black Guillemot eggs are a dull white or pale green colour and covered in dark spots and blotches. The colour and markings on the egg act as a near perfect camouflage to keep them safe from predators in the nest.
Each egg is around 59 x 40 mm in size and weighs around 50 grams with 8% of that weight being the shell.
How Long Do Black Guillemot Eggs Take To Hatch?
The eggs are incubated by both parents and hatch after around 28 to 32 days. The incubation is continuous with both parents taking it in shifts to attend to the eggs and go off to forage for food.
Chicks
After the incubation period comes to an end, we move on to the next stage in the life cycle of the Black Guillemot, the chicks.
How Many Chicks Does A Black Guillemot Have?
The number of chicks typically matches the number of eggs laid. Most parents have 2 chicks to raise although in some cases, there is only 1 and in others there are 3.
More experienced birds often start breeding earlier in the season and are more likely to have a larger brood. Unfortunately, the more chicks that successfully hatch, the more chance of chick mortality as siblings can become aggressive from around days 4 to 12.
When Do Black Guillemot Chicks Open Their Eyes?
Black Guillemot chicks are semi-precocial and can take 3 to 4 days to fully hatch. Once they do leave the egg, the chicks are covered in black down and have their eyes open and can wander around the nest.
They are fed by both parents right up until the chicks fledge. During this time, the parents take turns staying at the nest and foraging for food.
When Do Black Guillemot Chicks Fledge?
Black Guillemot chicks typically fledge or take their first flight anywhere between 30 to 40 days after hatching.
Once the chicks fledge they are completely independent and will typically return to the same breeding area once they reach the age of around 4 years to raise their own chicks.
SEE ALSO: Pied Wagtail Life Cycle: Nest Building To Fledging (and everything in between)
Frequently Asked Questions
The average lifespan of a Black Guillemot is around 11 years. However, there have been individuals that have survived for around 24 years according to ring data.
Black Guillemot eggs are a dull white or pale green colour and covered in dark spots and blotches. Each egg is around 59 x 40 mm in size and weighs around 50 grams.
The summer plumage of the Black Guillemot is completely black apart from a white patch on each wing. In winter they lose much of the black plumage which is replaced by white underparts and a mottled grey back and head.
