Cassia crossbill rarely interbreeds with other call types that move into the South Hills of Idaho yearly, and can be considered to represent a distinct species via ecological speciation. They tend to be in older, more open patches of lodgepole pine where they can find older cones that are easier to open. Unlike the nomadic Red Crossbill, the Cassia stays put year-round in a single county in Idaho, feeding on lodgepole pine cones that the Red Crossbill can't open.  The seeds of younger serotinous cones (1–10 years) are harder for the crossbill to pry open due to them being strongly bonded together. And it is their absence that favored the development of lodgepole pine cones that need fire and high temperatures to open. Additionally and related to their sedentary lifestyle and regular breeding cycle, the Cassia …  In 2007, some analyses found that different call types were genetically different including the South Hills crossbill (call type 9). Finches, Euphonias, and Allies(Order: Passeriformes, Family:Fringillidae).  A primary reason why this species of crossbill can exist in such a small area and on a singular food source is due to the lack of squirrels, the usual primary seed dispersal of the lodgepole pine.  The idea of reproductive isolation between call types was suggested, but direct evidence was lacking. This tit-for-tat between the lodgepole pine and the crossbill is called an evolutionary arms race. , As mentioned previously, the red crossbill had 10 different call types and the Cassia crossbill was call type 9. These two mountain ranges are unusual in having no red squirrels, which feed heavily on pine cones elsewhere. Idaho Birds offers site-specific information on where to find Cassia Crossbills. , The Cassia crossbill and the other red crossbill call types will strongly associate with their own call types.  The species may already lose potentially half its population due to the pending consequences of the 2020 Western United States wildfires, one of which engulfed a large portion of the South Hills, one of the only two strongholds for the bird. This has led to a coevolutionary arms race be… Although its relatives wander far and wide, the Cassia crossbill doesn’t stray from the lodgepole pine forests of Idaho’s South Hills and Albion Mountains. It is endemic to the South Hills and Albion Mountains in southern Idaho. Crossbills also need a bit of salt in their diet and seek out salt found in clay that hangs from the roots of upturned trees.  A major threat to the crossbill is climate change. A primary reason why this species of crossbill can exist in such a small area and on a singular food source is due to the lack of squirrels, the usual primary seed dispersal of the lodgepole pine.  In contrast, adult females have an overall dull green or olive-yellow colour, with brown flight feathers. The Cassia crossbill looks very much like a red crossbill, and it wasn’t officially recognized as a separate species until 2017. , The Cassia crossbill will exclusively forage for lodgepole pine cones that are found in the South Hills and Albion Mountains region.  Between 2001 and 2006, less than 1% of Cassia crossbills paired with other call types. Cassia Crossbill by Zak Pohlen | Macaulay Library, primer on identifying crossbill call types. The Cassia Crossbill, a finch with a crisscrossed bill, is closely related to the widespread Red Crossbill and was recognized as a full species in 2017.  Its body mass ranges from 29.2–43.9 g, while its wing length 85.0–100.0 mm and bill depth 8.90–10.56 mm. Formerly considered a localized form of Red Crossbill, the Cassia Crossbill was officially recognized as a full species in 2017.  Initially, it was considered one of the Red Crossbills’ 10 call types, which had different vocalizations, bill size and were foraging for different conifer species.  The crossbill will use its beak to pry the cone open and then it will use its tongue to obtain the seed.  Females will lay 2–6 eggs and they will incubate the egg for 12–16 days. Cassia Crossbills occur only in Idaho's South Hills and Albion Mountains, so you'll have to head there to see one.  This has led to a coevolutionary arms race with the lodgepole pine, which explains why they are confined in such a small area. Get Instant ID help for 650+ North American birds. , The Cassia crossbill (Loxia sinesciuris) was first described in 2009 as the South Hills crossbill, but The American Ornithologists' Union (AOU) failed to find consensus on the issue of splitting the species from the red crossbill in 2009.  In result, the lodgepole pine are creating cones with thick-scaled cones, whilst the crossbills have evolved deeper bills to counter this. The Cornell Lab will send you updates about birds, birding, and opportunities to help bird conservation. It lives only in lodgepole pine forests of the South Hills and Albion Mountains in Cassia County, southern Idaho.  It is the older and weathered cones that are more readily accessible as the scales begin to separate.  The individual notes of the song are typically buzzier and will have multiple instances of silence in between call phrases. eBird also has a primer on identifying crossbill call types.  Their song consists of strained and sharp chip and kip calls. The species' small population and geographic isolation makes it vulnerable to extinction. Squirrels are a common sight in many forests, but not in the lodgepole pine forests of Idaho's South Hills and Albion Mountains.  However, under the IUCN Red list criteria, it qualifies to be considered critically endangered due to its limited home range, small population and probable habitat degradation. The Cassia Crossbill was only recently determined to be a separate species, distinct from the common Red Crossbill that lives across the Intermountain West, a few years ago, and there is still much about the species that remains a mystery.  Due to their restricted range and habitat, there is a cause for concern for this species survival.  It is projected that the lodgepole pines will disappear from the South Hills and Albion Mountains by the end of the century. But researchers discovered that it doesn't breed with other crossbills, has a thicker bill, and isn't nomadic.  As a result, serotinous cones are especially abundant in this region, which allows cones with seeds to accumulate in high quantities that will last for decades. Luckily, unlike other crossbills, they are year-round residents, which makes finding them a lot easier. , The species was first described in 2009, but only was accepted to be its own species in 2017, when it was found out to be phylogenetically distinct from the red crossbill, and its 10 unique call types.  This eventually led to assortative flocking when crossbills would follow vocalizations that would provide them the easiest route to food. The crossbill will then use a groove inside its mouth to shell the seed to eventually eat it. The Cassia Crossbill also differs from Red Crossbill through shifted and set phenology of life history events.