All About Crossbills - Crossbill Facts & Information

Crossbills are a medium-sized finch, recognised for their distinctive crossed bill. This bill allows them to extract seeds like an expert!

Males are brightly coloured, usually orange-red in colour, while females are a more subdued olive green colour. 

Some Common Crossbills migrate widely based on conifer cones abundance, a behaviour known as "irruptive migration." These movements, based on food availability, can bring them far from their usual habitats. In the UK, they are the only endemic bird species.

Crossbills are often easier to identify by sound than sight. They have a distinct "jip-jip" or "chup-chup" flight call, which can help distinguish them from other finches.

In the UK, there are two main separate species of Crossbills:

Common Crossbill 

(Loxia curvirostra): Found across the UK, mainly in Scotland and parts of northern England.

Scottish Crossbill

(Loxia scotica): Endemic to the Caledonian pine forests of Northern Scotland, making it the UK’s only truly native bird species. This crossbill is nearly identical to the Common Crossbill, but has a slightly different call and is often considered a distinct species.

The Parrot Crossbill

The Parrot Crossbill (Loxia pytyopsittacus) is a larger, rarer relative of the Common Crossbill, notable for its thicker, more robust beak designed to handle tougher pine cones. It is mainly found in Scandinavia but occasionally migrates to the UK, particularly Scotland and parts of northern England, during "irruptions".

Both species can be challenging to differentiate by sight alone due to their similar appearance, but they can be identified through their calls and habitats. There is also a third species, called the Parrot Crossbill.

Habitat

Crossbills are highly specialised birds with unique habitat needs centred around their dependence on conifer trees. In the UK, two main habitats are critical for sustaining crossbill populations: coniferous woodlands and, specifically for the Scottish Crossbill, Scotland’s ancient Caledonian pine forests.

Common Crossbills are typically found in conifer-rich areas throughout the UK, particularly in Scotland, Northern England, and Wales. They are also occasionally seen in Southern England, especially when food supplies are limited in northern regions.

They thrive in mixed and dense coniferous forests where pine, spruce, and larch trees dominate. They’re particularly attracted to mature forests with large numbers of cone-bearing trees, as these provide ample food throughout the year.

While Common Crossbills are mostly resident in the UK, they are nomadic and may travel extensively depending on conifer seed production. This irruptive behaviour leads them to shift habitats, sometimes covering long distances to find food sources.

Diet

Seeds found in pine cones, particularly Scots pines, are a favourite food for the Crossbill. Their powerful, crossed bill allows them to twist open the tough cone and reach the seeds within. 

When pine seeds are scarce, crossbills turn to other conifers, such as spruce and larch. These trees provide additional options, helping crossbills maintain their food supply through different seasons.

During the colder months, when other food sources are scarce, crossbills primarily depend on conifer seeds. This time of year often has the highest availability of cones, which provides abundant food.

Though conifer seeds remain a primary food source, Crossbills may supplement their diet with other items, such as buds, young shoots, and even insects. These additions provide essential nutrients, especially during the breeding season.

Crossbills have an unusual breeding cycle for UK birds; they often breed in late winter or early spring, coinciding with peak seed availability in conifer forests. Seeds from cones are essential during this time, providing the energy needed for both adults and their chicks. Parents feed their young almost exclusively on seeds, softened and regurgitated, making a plentiful supply of conifer seeds critical to reproductive success.

Breeding Season 

The breeding season of crossbills in the UK is unique among birds, as they often begin nesting in late winter. Rather than waiting for warmer spring months like most birds, crossbills start breeding as early as January or February, capitalising on the abundance of conifer seeds in winter. 

This early breeding allows them to rear their young when food sources are plentiful, as pine and spruce cones are full of seeds during this time. If seed availability remains high, Crossbills may continue nesting into the spring or even early summer, potentially raising multiple broods in a single season.

During courtship, adult males put on display flights and sing to attract mates, showing off their bright plumage, males are often a striking red, while females are more subdued. Once paired, crossbills form monogamous bonds for the season, with both parents involved in raising their young. 

They typically build their nests high in conifer trees, close to the trunk, where branches offer stability and shelter from cold winds. The nest is crafted from twigs, moss, and lichens, with a soft lining of feathers to provide warmth, as temperatures can be harsh during the winter months.

A typical clutch consists of 2-4 eggs, which are incubated by the female while the male forages and brings food back to her. The incubation period lasts around 12-14 days, after which the chicks hatch and both parents take turns feeding them. 

The chicks rely on a diet of regurgitated conifer seeds, which provide the high-energy nutrients needed for rapid growth. This dependence on seeds highlights why breeding is so closely timed with cone abundance. The chicks remain in the nest for about 18-24 days, after which they fledge but may still rely on their parents for additional food as they learn to forage.

Predators and threats

One of the primary threats to Crossbills is habitat loss. Conifer woodlands, particularly the Caledonian forests, face pressures from commercial logging, land development, and agricultural expansion. In many parts of the UK, non-native conifer plantations are also harvested regularly, which can disrupt crossbill habitats and reduce the availability of mature trees with abundant cones. This loss of habitat has a significant impact on crossbill populations, as their specialised diet of conifer seeds ties them to these woodlands.

Climate change is another major challenge for crossbills. As temperatures rise and weather patterns become more unpredictable, cone production in conifers can be affected, leading to fluctuations in the food supply. Crossbills rely on a stable supply of conifer seeds to support their unique breeding cycle, which often begins in late winter. If climate change results in fewer or less predictable cone crops, crossbill populations may experience declines due to food shortages, especially during critical breeding periods. 

Predation and competition also pose threats, particularly to eggs and young birds in the nest. Crossbill nests, though well-hidden high up in conifer trees, are still vulnerable to predation by species like jays, crows, squirrels, and other woodland animals. In the absence of sufficient food in their natural habitats, crossbills may sometimes encounter increased competition from other bird species for food sources, particularly in fragmented forests where resources are limited.