Cassia Crossbill Care Sheet

Scientific Facts

Common NameCassia Crossbill
Scientific NameLoxia sinesciuris
SizeNo data available
Mass29.2–43.9 grams
HabitatForests dominated by mature lodgepole pine trees
DistributionSouthern Idaho: South Hills and Albion Mountains

Information & Physical Description

Scientifically referred to as Loxia sinesciuris, the cassia crossbill is classified as part of the family Fringillidae, subfamily Carduelinae. The physical appearance of this small-sized, yet stocky passerine bird has many common features with the physical appearance of the red crossbill (Loxia curvirostra).

Apart from sharing numerous similar physical attributes, the different call types that are typical for red and cassia crossbills are also the same.

Adult male cassia crossbills differ from adult female cassia crossbills.

Mature males are characterized by flight feathers colored in brown, and a brick-red plumage that runs along the belly, breast, and crown, displaying a patchy mix of oranges, yellows, and crimson reds. The tail is notched.

On the other hand, the plumage of mature females displays olive-yellow or dull green coloration overall, with the flight feathers being brown in color, just like in males. It is in the belly zone where females exhibit more of yellow coloration.

Immature cassia crossbills resemble the physical appearance of adult females; however, the breast of the young is streaked.

Even though small in size, and despite the fact that there is no data available on the exact size attained by cassia crossbills, these birds are described as smaller than the Evening grosbeak, yet bigger than the Cassin’s Finch.

The defining feature of the cassia crossbill is none other but the peculiar, specialized crossed bill. The bill is described as a crisscrossed bill. It is used for the purpose of accessing pine cone seeds.

The bill of the cassia crossbill is significantly thicker and deeper than the bill of the red crossbill, and it is thanks to the thickness and depth of the bill how these birds manage to crack open the much harder types of pine cones found in its natural habitat.

The bill depth of Loxia sinesciurisis estimated at 8.90–10.56 mm., while the wing length is estimated at 85.0–100.0 mm.


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According to the Animal Ageing and Longevity Database, cassia crossbills’ close relative, the red crossbill, has been found to live up to 8 years in captivity, while the maximum recorded lifespan of a wild red crossbill is 16 years. However, when it comes to the lifespan of cassia crossbills, currently, there is no data available.

Ecosystem & Habitat

The Cassia crossbill is a non-migratory bird. It is found exclusively in Southern Idaho, and in particular, in the forests of the Albion Mountains and the South Hills, where it resided all year-round.In comparison to its global species counterpart, the red crossbill, Loxia sinesciuris species reside in an area that measures about 67 square kilometers.

Because of being “equipped” with a highly specialized, well-adapted beak to feeding on a specific type of pine cone, the cassia crossbill is known to exclusively occur in open forests greatly dominated by old-growth, mature lodgepole pine (Pinus contorta, aka contorta pine or twisted pine), where no Red Squirrels are found.

Being adapted to feeding on Pinus contorta pine cones, experts are now certain that the reason why cassia crossbills are confined to such a small area is none other but the co-evolutionary, deep ecological relationship they share with the lodgepole pine.

Unfortunately, it is exactly because of their rather restricted habitat and range of why there is a cause for concern when it comes to the survival of Loxia sinesciuris. Furthermore, this bird species is very poorly adapted to feeding on other pine cones in the nearby surroundings.


The red crossbill is estimated to have 10 different call types. Meanwhile, the cassia crossbill is estimated to fall into the call type 9 category.

Loxia sinesciuris fledglings are known to imitate their parents’ flight calls. Later on, fledglings are to modify their calls to imitate their mates.
The cassia crossbills songs tend to be more repetitive, as compared to other call types. Also, their songs consist of fewer syllables.

Furthermore, the individual notes of the cassia crossbills’ songs have numerous instances of silence that take place between call phrases. In addition to that, the individual notes are usually buzzier.

A combination of kip calls and the sharp and strained chip is what the song of the cassia crossbill consists of.

Cassia crossbills have different excitement calls as compared with red crossbills. These excitement calls are given in response to aggressive mates in the flock, or as an alarm call. The cassia crossbill’s excitement call is described as a call that rises and subsequently falls in pitch.

Sometimes, it is possible for red crossbills engaged in foraging to overlap between the different call types.

In fact, it is suggested that crossbills used different calls as a source of public foraging-friendly information. Eventually, this is believed to have led to assertive flocking.

In assertive flocking, crossbills follow vocalization in order to be able to find the easiest food route to follow. Ultimately, this is thought to be another possible mechanism through which the cassia crossbill has diverged from its counterpart, the red crossbill.

Up-to-date, despite being classified as a distinct species, the Cassia Crossbill still shares much of the pretty same behavior typical for the Red Crossbill.Both of these bird species are known to forage in large groups. Also, the large groups these birds form when foraging are vocal, too. The red and the cassia crossbills alike do not only eat seeds directly from the pine cones located in the canopy but do forage for seeds that have fallen on the ground.

Contrary to the red crossbills, though, the cassia crossbills are rather sedentary birds. They do not wander, but instead, they breed at the same time and the same area year after year.

Groups of Cassia Crossbills can be spotted flying by following an undulating pattern while searching for a nice cone crop in the lodgepole forests. Dangling from branches and cones, their crisscrossed bills allow them to extract the delicious seeds.

Food & Diet

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The Cassia crossbill is known to forage exclusively for lodgepole pine cones. These are found only in the Albion Mountains and the South Hills region in southern Idaho.
According to experts, the major reason why the cassia crossbill is capable of existing in such a confined, small-sized area while feeding solely on a singular food source, is thanks to the absence of squirrels, as it is usually squirrels to be the primary lodgepole pine’s seed dispersal.

Due to the lack of squirrels in the cassia crossbill’s habitat, serotinous cones are abundant in the Albion Mountains and the South Hills region. The abundance allows cones rich in seeds to gradually accumulate in high quantities, and these quantities are enough to last for decades.

The special ecological relationship that the cassia crossbill and lodgepole pines share has led to a coevolutionary arms race between these two species, with the cassia crossbill species being the major selective agent.

As a result of this amazing ecological relationship, lodgepole pines keep creating unique cones characterized by thick scales. In the meantime, the cassia crossbill has kept evolving a deeper bill in order to counter the tough-scaled cones.

Interestingly, younger serotinous cones aged 1 and up to 10 years are actually much harder to pry open, and that’s because these are bonded together strongly. However, the weathered, older cones are characterized by scales that gradually begin to separate, thus, being more readily accessible to the cassia crossbills to feed with.

Cassia crossbills are known to mainly feed on cone seeds by extracting these right on the pine tree itself, but these birds will also forage fallen cones, too. The way cassia crossbills feed is by using their beaks to pry the cone open. Next, the birds’ tongues are utilized for the purpose of obtaining the seed.

Finally, the crossbill is to make perfect use of the groove located inside its mouth in order to shell the seed before eventually eating it.


The breeding season for cassia crossbills starts in late March and up to early April. It is around late July when the breeding season ends.

Male cassia crossbills will court females by flying above the forest canopy, as well as with a song. Additionally, males will continue to court females by gently feeding them delicious pine seeds.

Breeding consistently throughout the year, unlike the opportunistic, nomadic red crossbill breeders, cassia crossbills are known to build a nest that resembles the shape of a cup. The nest is made out of grasses, needles, and twigs.

Females are the ones to do the majority of nest building, yet males do also help occasionally.

After copulation is to successfully occur, the males are to aggressively defend their female partner from other possible breeding males. Laying between two and up to six eggs varying from pale pink to white to pale green in color, it is the females’ responsibility to incubate the eggs. Incubation lasts for 12 and up to 16 days.Nesting takes 15 and up to 25 days, with the hatchling being helpless and naked upon hatching.

The young are fed by regurgitation. The parents share feeding responsibilities, as both males and females are to regurgitate a smooth paste consisting of saliva and lodgepole pine seeds. The young chicks are fed up until they are old enough to consume whole seeds on their own.

Survival Threats & Conservation

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Currently, the total population of cassia crossbills is estimated at about 5800 individuals.

Based on the IUCN Red List of Threatened species assessment criteria, the cassia crossbill does qualify to be considered critically endangered, and that’s because of these birds’ small population, probable habitat degradation, as well as their rather limited home range. However, since the Loxia sinesciuris actually has the status of a new species, it is not possible for the conservation status to be assessed as of now.

The major survival threat to the cassia crossbill is none other but climate change. Due to cumulative hot weather, with temperatures exceeding 32 degrees Celsius, the pine cone seeds disperse earlier than usually. The early dispersal leads to limited food availability, as these birds rely on feeding with lodgepole pine cones all year-round.
In addition to that, warmer weather resulting from the changes in climate leads to increased rates of mountain pine bark beetle infestations.

Pine bark beetles are known to burrow in the pine trees, eventually leading to the trees being killed over time, and this is related to further exacerbating the food availability and security issues for cassia crossbills.

Not the least, another of the threats posed by climate change is the increased potential for large fires. Large fires can certainly prove disastrous for the population of cassia crossbills in the case a big number of lodgepole pine trees get to burn and die in flames.

Furthermore, according to projections, lodgepole pines are estimated to fully disappear from the Albion Mountains and the South Hills by the end of the century.

The populations of cassia crossbills have suffered a great decline, even though recently they have increased a little.

According to Chris Benkman, who is an ecologist in the University of Wyoming, and has teamed up with Nathaniel Behl to publish a 2016 paper estimating the population of Cassia Crossbill, conservation efforts may help to save this unique bird species from extinction, even though the maintenance of mature lodgepole pines providing plenty of old, closed cones, is certainly going to be “very challenging”.

However, Benkman further highlights that despite being a challenging task, the conservation of this bird species is “likely worthwhile” the concerted efforts, as the forests where cassia crossbills thrive, do provide much more than just a wonderful habitat to these feathery living creatures, but instead, the forests make up for the crucial biodiversity and balance on the planet, relating with the well-being of mankind in sacred, complex, ancient ways.

Availability – Where to Get a Cassia Crossbill

One cannot get a Cassia Crossbill in the sense of getting to take care of the bird as a pet. Cassia crossbills are wild, range-restricted birds, and are not kept as pets. If you come across online or offline retailers offering you Cassia crossbills for sale, please, immediately contact a conservation officer. Even though one cannot care about the Cassia crossbill as a pet, it can be a wonderful idea to go bird watching these amazing feathery creatures in their natural habitat.

These birds are known to occur only and solely in Idaho’s South Hills and Albion Mountains. With that being said, it is to this particular region where one needs to head to in order to see a cassia crossbill in the wild.

Fortunately, as cassia crossbills are year-round residents of the Albion Mountains and South Hills in southern Idaho, finding them is usually much easier, as opposed to finding other crossbills that live nomadically.

Look for the cassia crossbill in the more open, older patches of the lodgepole pine forest, as these are preferred by Loxia sinesciurisspecies,because of these forests being more abundant in weathered, old cones that are easier to crack open.

Additionally, prior to hiking into these birds’ range, mind that you stand higher chances of getting a glimpse of these feathery fellows, provided you are well-familiar with their unique call type. To understand the cassia crossbills call better, you can study it up in advance by conducting some proper research.

Note that even though the best way to separate Red from Cassia Crossbills is by voice, this isn’t really an easy-peasy task to accomplish, and further analyses of a recording are often necessary to be able to distinguish between these birds.

While the cassia crossbills’ call differs slightly from that of red crossbills, hearing the difference is quite challenging, yet it is good to remember that the call of cassia crossbills is slightly lower in pitch, and with a harsher quality as compared to the call of the red crossbills

Interesting Facts

1. The Cassia Crossbill was first described back in 2009. However, it wasn’t before 2017 when it was officially accepted as a separate species of its own after experts managed to find out that the Cassia crossbill is phylogenetically distinct from the red crossbill.
2. Other red crossbill call types, and in particular, most commonly call type 2 and call type 5, are also known to occur in the same areas where the cassia crossbill thrives. However, other red crossbills will rarely breed in the regions inhabited by cassia crossbills, since red crossbills are very poorly adapted to feeding on the specifically structured pine cones of lodgepole pines.
3. The cassia crossbill was first named the South Hills crossbill when it was described in 2009. However, the AOU (American Ornithologists’ Union) failed to find an answer regarding the issues of possibly splitting this bird species from the red crossbill.

Initially, the cassia crossbill was considered one of the 10 call types of Red Crossbills, characterized by different vocalization, different preferred types of conifer species to feed on, as well as a different bill size.Even though the idea of existing reproductive isolation between call types was suggested back then, any direct evidence was still lacking, yet in 2017, researchers managed to discover that different call types are actually genetically different, based on analyses. This was exactly the case with the South Hills crossbill considered as call type 9.

As evidence further suggested that the coevolutionary arms race between the South Hills crossbill and the lodgepole pine has led to habitat isolation, the cassia crossbill was finally identified as phylogenetically different, distinct from any other crossbill call types in 2016. It is the tit-for-tat between the crossbill and the lodgepole pine that is referred to as an evolutionary arms race since instead of being deterred by the pine’s protective measures, the cassia crossbill has slowly and successfully evolved a thicker bill in order to get access to the seeds.

Nowadays, cassia crossbill is considered a perfect example of sympatric speciation.

4. The genus “Loxia” translated into “crosswise,” referring to the peculiar bill of cassia crossbills. Meanwhile, sinesciuris” translates into “without squirrel.” Loxia sinesciuris species have managed to evolve because of the absence of the squirrels in the lodgepole pine forests.

5. Cassia crossbills need a bit of salt in their diet. Because of this, they seek out soil available in clay hanging from upturned trees’ roots.

How to Care for the Cassia Crossbill

The best way to care for the Cassia Crossbill is to understand the collective responsibility that all human beings share with putting intentional efforts when it comes to blocking the further development of the negative changes in climate.

By spreading awareness over the consequences of climate change, as well as by choosing an environmental-friendly lifestyle, every person is able to take personal care to improve the health and well-being of the living nature, including the well-being and future survival of the Cassia Crossbill.

To limit your carbon footprint on Mother Nature, as this is the leading cause for climate change, you can choose to refuse single-use, to reduce consumption, to reuse everything possible whenever possible, to refurbish old stuff, to choose to travel by bike, by foot, or by using public transport as much as feasible, to repair anything before replacing it with a new belonging, to be creative and repurpose various stuff by reinventing them instead of throwing these to the trash, and nonetheless, to recycle.

In addition to that, it is possible to volunteer in wildlife conservation programs.

FAQ Section

What Does the Cassia Crossbill Look like?

The Cassia Crossbill, greatly resembling the Red Crossbill, is a small-sized, stocky passerine bird with a crisscrossed bill. Adult male Cassia crossbills have a patchy mixture of yellows, reds, and orange, while adult females are overall dull green to hues of olive-yellow in color.

Is the Cassia Crossbill Endangered?

Even though it is not yet assessed by the IUCN Red List of Threatened Species because of being recently described as a distinct species, the Cassia Crossbill does fit into the category of critically endangered birds by major criteria, such as its limited geographic distribution and habitat degradation related with the consequences of climate change.

What Does the Cassia Crossbill Feed with?

The Cassia Crossbill feeds exclusively with lodgepole pine cones, using its well-adapted bill to crack the hardy shell of the cones open.

Where Does the Cassia Crossbill Live?

The Cassia Crossbill only lives in a restricted region in Southern Idaho where lodgepole pine trees grow, namely the Albion Mountains and the South Hills.

Do Cassia Crossbills Migrate?

No, Cassia Crossbills do not migrate. These birds reside in the lodgepole pine forests in Southern Idaho, all year-round.

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