Crossbill (Loxia spp) Species Guide: Appearance, Diet, Habitat, Behavior, Stats, And Conservation Status

Species Guide | Crossbill (Loxia spp).

The Crossbill consists of six official species, three of which are UK resident:

• Scottish Crossbill (Loxia scotica) [UK Resident]
• Parrot Crossbill (Loxia pytyopsittacus) [UK Resident]
• Red Crossbill or Common Crossbill (Loxia curvirostra) [UK Resident]
• Two-Barred Crossbill (Loxia leucoptera)
• Hispaniola Crossbill (Loxia megaplaga)
• Cassia Crossbill (Loxia sinesciuris)

The Scottish Crossbill is badged as the UK’s only endemic species, after being classified as a separate species in the 1980s. At the time, it was argued that they had genetically diverged due to geographical isolation. However this was disproved as the same genetic variability such as larger bills exists across all Crossbill populations, and there is no geographical isolation as Crossbills are known to migrate. Indeed genetically it is impossible to differentiate between the Common Crossbill, Parrot Crossbill, and the Scottish Crossbill. The result is that there has been pressure to de-classify the Scottish Crossbill.

It is also argued that whilst there may not be any visible genetic differences, the Scottish Crossbill has specific vocalizations that differentiate it. Similar observations on different calls within Crossbill populations have been made in the USA, where it has been identified that there are multiple regional variations¹. Birds are known to learn new calls & vocalizations², though some research from 2007 claimed that this is rare, and females from these pockets of Crossbills ignore the calls of males without the unique call signs. Therefore interbreeding amongst the pockets of birds is argued to be limited³. The most interesting development on Crossbill calls was in 2022, when the Scottish Birds Records Committee conducted a detailed analysis of sonogram recordings of Common Crossbills and Crossbills from Scottish regions, concluding that no evidence suggests the calls differed⁴. Indeed, they specifically state that:

“SBRC is no longer aware of any plumage, biometric, vocal or genetic criteria that can be used to identify Scottish Crossbill with confidence. As a result, SBRC will no longer consider any records of the species”.

This is perhaps the strongest statement so far from an official body. In conclusion, the Scottish Crossbill may well be nothing more than an urban myth, with all evidence pointing towards that they are Common Crossbill.

However, this still leaves the question as to whether Common Crossbills and Parrot Crossbills are the same species. Perhaps the recent declassification of three species of Redpolls into one species is an indication of things to come! Check out our Redpoll Species Guide for more information.

This article is about the U.K. resident Crossbills and assumes a lumping together of the UK resident species into Crossbill (Loxia spp).

APPEARANCE

The Crossbill is a member of the finch family of birds. They look quite chunky compared to most of their cousins, with a large head and a distinctive bill. Adult males have a brick-red coloration, while females have a greenish-brown hue.

Diet

Their preferred food is the seeds from conifer cones, and is the explanation for the Crossbills’ unique bill shape, as the bill structure allows them to readily extract seeds from the cones. They will also eat buds and shoots from other plants, and will even eat insects, especially during the summer months when insect populations soar.

HABITAT

Crossbills inhabit coniferous habitats throughout the British Isles. They are both a resident species and a partial migrant; driven by the availability of conifer seeds in their favored feeding grounds.

Note that this map is for a rough illustration of animal distribution across the UK⁵, whereby light green indicates established populations.

Behavior

Crossbills are often found in flocks, of family members and larger groups. They are typically at treetop height; close to their food source. They have a distinctive call which is relatively easy to distinguish from other finches.

Crossbills sometimes start breeding during the winter months if there is plenty of food available, but will typically breed during the summer months. They nest in conifer trees, building a small cup from twigs and moss, and then lined with fur. The nest consists of 3 to 4 eggs which hatch after approximately 2 weeks, and fledge after a further month.

STATS

NATURAL PREDATORS

Sparrowhawks are their main predators. The nests are vulnerable to a range of predators including some mammals.

Conservation Status

It is estimated that there are more than 26 thousand pairs in the British Isles alone. They are green-listed in the UK and registered as Least Concern from a global conservation standpoint by the International Union for Conservation of Nature (IUCN). It should be noted however that Parrot Crossbill is UK Amber listed.

U.K.
Conservation Status

Global
Conservation Status

References

1. Young MA, Spahr TB, McEnaney K, Rhinehart T, Kahl S, Anich NM, Brady R, Yeany D and Mandelbaum R (2024) Detection and identification of a cryptic red crossbill call type in northeastern North America. Front. Bird Sci. 3:1363995. doi: 10.3389/fbirs.2024.1363995
2. British Ornithologists Union
3. Summers, R. W.; Dawson, R. J.; Phillips, R. E. (2007). “Assortative mating and patterns of inheritance indicate that the three crossbill taxa in Scotland are species”. Journal of Avian Biology. 38 (2): 153–162. doi:10.1111/j.0908-8857.2007.03798.x.
4. Lewis, M. & McInerny, C.J. 2022. SBRC position on Scottish Crossbill. Scottish Birds 42: 71-72.
5. Population data based on BTO assessment
6. Featherbase
7. British Trust For Ornithology