Marsh Harrier Life Cycle: Nest Building To Fledging (and everything in between)
The Marsh Harrier (Circus aeruginosus) is a magnificent bird of prey that has made a remarkable comeback in the UK after nearly becoming extinct in the 1970s. These impressive raptors are known for their distinctive V-shaped wing posture during flight and their remarkable hunting skills over wetlands and reed beds.
Marsh Harriers are a testament to successful conservation efforts, with their population rebounding from just a single breeding pair in 1971 to over 400 breeding pairs today. Their recovery story is one of the most inspiring in British wildlife conservation history.
In this article, we’ll explore the fascinating life cycle of the Marsh Harrier, from nest building to the fledging of their young, uncovering the secrets of their breeding success and survival strategies.
Table of Contents
How Long Does A Marsh Harrier Live?
Marsh Harriers typically live for about 6 to 8 years in the wild. However, with favourable conditions and absence of threats, they can potentially live longer.
The oldest recorded Marsh Harrier in the wild lived to be 16 years old. This longevity is quite impressive for a medium-sized bird of prey, especially considering the various challenges they face in their wetland habitats.
Several factors influence a Marsh Harrier’s lifespan, including food availability, habitat quality, and human-related threats such as pollution and habitat destruction. Their ability to adapt to different prey and habitats contributes to their survival.
How Fast Can A Marsh Harrier Fly?
Marsh Harriers can fly at speeds of up to 30 to 40 miles per hour (48 to 64 km/h) when pursuing prey or during territorial displays. However, their typical cruising speed is much slower, around 20 to 30 miles per hour (32 to 48 km/h).
These birds are not built for high-speed pursuits like some falcons. Instead, they are adapted for efficient, low-altitude flights over marshes and reed beds. Their broad wings and light build allow them to glide and soar with minimal effort, a useful trait for scanning large areas for prey.
Marsh Harriers have a distinctive flight pattern, often holding their wings in a shallow ‘V’ shape. This posture, known as a dihedral, provides stability and lift, allowing them to fly slowly and steadily over their hunting grounds without stalling.
Are Marsh Harriers Aggressive?
Marsh Harriers are generally not aggressive towards humans but can display territorial behaviour during the breeding season. They are known to vigorously defend their nesting sites from other birds of prey and potential predators.
During courtship and pair formation, male Marsh Harriers perform spectacular aerial displays, which can include aggressive chases and mock fights with other males. These displays, while appearing aggressive, are usually more about showing off flying skills and establishing dominance than actual combat.
Towards other species, Marsh Harriers can be quite assertive, especially when hunting. They have been observed chasing off larger birds from prime hunting spots and even stealing prey from other raptors, a behaviour known as kleptoparasitism.
What Is A Marsh Harrier’s Habitat?
As their name suggests, Marsh Harriers are primarily associated with wetland habitats. They prefer large reed beds, marshes, and wet grasslands near lakes, rivers, and coastal areas.
In the UK, Marsh Harriers are most commonly found in eastern England, particularly in areas like the Norfolk Broads, Suffolk coast, and parts of Kent and Somerset. They have also begun to colonise some inland wetlands as their population has recovered.
These birds require a mix of open water, dense vegetation for nesting, and surrounding areas with abundant prey. While they primarily hunt over wetlands, they also forage over adjacent farmland, especially during winter when their wetland prey may be scarce.
How Long Does It Take For A Marsh Harrier To Build A Nest?
Marsh Harriers typically take about 1 to 2 weeks to build their nests. The nest construction is primarily carried out by the female, with the male bringing most of the materials.
The nests are usually built on the ground or just above water level in dense vegetation, particularly in reed beds. They are large structures, and the outer structure is made of sticks and reeds, while the inner cup is lined with softer materials like grass and leaves.
Marsh Harriers often return to the same nesting area year after year, though they typically build a new nest each breeding season. This behaviour helps them adapt to changing water levels and vegetation growth in their wetland habitats.
Eggs
The egg-laying process is a crucial stage in the Marsh Harrier’s breeding cycle. Let’s explore the details of their eggs and laying habits.
When Do Marsh Harriers Lay Eggs?
Marsh Harriers typically lay their eggs between mid-April and early June in the UK. The exact timing can vary depending on factors such as weather conditions and food availability.
In some cases, particularly if the first clutch is lost early in the season, Marsh Harriers may attempt a second clutch. However, this is relatively uncommon, and most pairs only raise one brood per year.
The timing of egg laying is crucial for Marsh Harriers. It’s synchronised with the availability of prey in their habitat, ensuring that there’s sufficient food available when the chicks hatch and need to be fed.
How Many Eggs Does A Marsh Harrier Lay?
A female Marsh Harrier typically lays between 3 to 5 eggs, although clutches of up to 6 have been recorded in exceptional cases.
The eggs are laid at intervals of about 2 to 3 days. Despite this staggered laying, incubation usually begins with the first or second egg, leading to asynchronous hatching of the chicks.
The number of eggs laid is often influenced by the availability of food in the surrounding environment. When food is abundant, larger clutches are more common.
What Do Marsh Harrier Eggs Look Like?
Marsh Harrier eggs are oval in shape and have a smooth, slightly glossy surface. They are primarily white or pale blue in colour, often without any markings.
The eggs measure about 48 to 54 mm in length and 37 to 41 mm in width. They weigh approximately 37 to 39 grams.
The pale colouration of the eggs serves a purpose in their wetland habitat. It helps to reflect heat, preventing overheating in the nest which can be exposed to direct sunlight in reed beds.
How Long Do Marsh Harrier Eggs Take To Hatch?
Marsh Harrier eggs typically take between 31 to 38 days to hatch, with an average incubation period of about 33 to 35 days.
Incubation duties are shared between both parents, although the female does the majority of the incubation. The male’s role is crucial during this period as he provides food for the female, allowing her to spend more time on the nest.
During incubation, the parents carefully turn the eggs several times a day. This movement is essential for the development of the embryo, ensuring even heating and preventing the embryo from sticking to the shell.
Chicks
The development of Marsh Harrier chicks from hatching to fledging is a fascinating process that showcases the dedication of the parent birds and the rapid growth of the young.
How Many Chicks Does A Marsh Harrier Have?
A Marsh Harrier pair typically raises 3 to 5 chicks per breeding season, corresponding to the number of eggs that successfully hatch and survive to fledging.
While clutch sizes can be larger, not all eggs always hatch, and not all chicks survive to fledging. Factors such as food availability, weather conditions, and predation can affect chick survival rates.
In years of abundant prey, more chicks are likely to survive, while in years of scarcity, the smallest or weakest chicks may not make it. This natural selection ensures that the fittest individuals survive to contribute to future generations.
When Do Marsh Harrier Chicks Open Their Eyes?
Marsh Harrier chicks typically open their eyes within 3 to 5 days after hatching. When they first hatch, the chicks are altricial, meaning they are born relatively underdeveloped, blind, and completely dependent on their parents.
The opening of their eyes marks an important milestone in their development. As their vision develops, they become more responsive to their surroundings and better able to beg for food from their parents.
It’s worth noting that even after their eyes open, the chicks’ eyesight continues to develop and improve over the next few weeks, gradually allowing them to observe and learn from their parents’ behaviours.
When Do Marsh Harrier Chicks Fledge?
Marsh Harrier chicks usually fledge (leave the nest) when they are about 35 to 40 days old. However, they remain dependent on their parents for food for several weeks after fledging.
The fledging process is gradual. In the days leading up to their first flight, the chicks can often be seen exercising their wings and making short hops around the nest area. Even after their first flights, they often return to the nest or stay close by, only gradually expanding their range.
During this post-fledging period, which can last up to 6 weeks, the young harriers learn crucial hunting skills from their parents. They practise flying and hunting techniques, preparing for independent life.
By late summer or early autumn, the young Marsh Harriers are usually fully independent. Some may disperse to new areas, while others may remain in their natal area if food resources are plentiful.
SEE ALSO: Marsh Harrier Diet and Size: Feeding Habits, Predators, and Measurements
Frequently Asked Questions
Marsh Harriers build their nests on the ground, often in dense reed beds or tall grasses. These nests are well-camouflaged, helping to protect their eggs and chicks from predators.
Marsh Harriers have a wingspan of 115 to 130 cm, which helps them glide gracefully over open landscapes in search of food.
Yes, Marsh Harriers are migratory birds. They typically migrate from the UK to southern Europe or Africa during the winter, returning to their breeding grounds in the spring.
While Marsh Harriers were once on the brink of extinction in the UK, they are no longer considered endangered thanks to successful conservation efforts. However, they are still relatively rare and are protected under the Wildlife and Countryside Act 1981.
