Quick Answer
Lesser and linnet redpolls are two closely related species of small finches in the genus Acanthis. The key differences between them are:
- Lesser redpolls have smaller bills and bodies and are paler overall compared to linnet redpolls.
- Lesser redpolls breed further north into the arctic tundra while linnet redpolls breed further south in boreal forests.
- Linnet redpolls have more streaking on their undertail coverts compared to lesser redpolls.
- The song and call notes of linnet redpolls sound deeper and huskier compared to the higher-pitched notes of lesser redpolls.
- There are identifiable genetic differences between lesser and linnet redpolls.
Taxonomy and Identification
Lesser and linnet redpolls are classified as distinct species within the genus Acanthis. The scientific names are:
- Lesser redpoll – Acanthis cabaret
- Linnet redpoll – Acanthis flavirostris
They were previously considered conspecific (the same species) but multiple lines of evidence support their separation:
- Genetic studies show consistent differences between lesser and linnet redpoll populations.
- Their breeding ranges overlap but they occupy different habitats (tundra vs. boreal forest).
- There are small but consistent differences in morphology and vocalizations.
Not all experts accept their split into two species, in part because lesser and linnet redpolls can interbreed where their ranges overlap. Some authorities still consider them conspecific. More research is needed to fully resolve their taxonomy.
Distinguishing lesser and linnet redpolls by sight can be challenging. In general:
- Lesser redpolls are smaller with more delicate bills, less streaking on belly and undertail coverts, and a pale brown (not rufous) back.
- Linnet redpolls are larger with bigger bills, more streaking below, and a rufous-toned back.
However, the features can be variable and intermediate birds occur. Sound recordings of their distinct vocalizations are the most reliable identification method.
Geographic Ranges
Lesser and linnet redpolls occupy overlapping breeding ranges across northern Eurasia and North America:
- Lesser redpolls breed further north into the arctic tundra zones of Europe, Asia, Alaska, and Canada.
- Linnet redpolls breed predominantly in the boreal forest zones south of the tundra.
During the winter, both species can irrupt southwards in large numbers if food is scarce. Their wintering ranges overlap extensively but lesser redpolls tend to move further south into temperate regions while linnet redpolls are more likely to remain in the boreal zone.
Here are the approximate breeding and wintering ranges:
Lesser Redpoll
Breeding: Arctic tundra zones of northern Europe, Asia, Alaska, Canada. South to Scotland, southern Scandinavia, northern Mongolia, British Columbia, Manitoba.
Wintering: Boreal forests and temperate regions including most of Europe, southern Canada, northern USA. Irruptions can reach the UK, Mediterranean, northeast USA, California, Carolina.
Linnet Redpoll
Breeding: Boreal forests of northern Europe, Asia, Alaska, Canada. South to northern UK, Baltic region, Siberia, Alberta, Ontario.
Wintering: Boreal forest across Eurasia, Alaska, Canada. Irruptions into temperate regions but not as far south as lesser redpolls overall.
So in summary:
- Lesser redpolls breed further north in the arctic tundra.
- Linnet redpolls breed predominantly in the boreal forest to the south.
- Lesser redpolls tend to move further south in winter compared to linnet redpolls.
Habitat Preferences
The habitats that lesser and linnet redpolls occupy during the breeding season differ in line with their ranges:
Lesser Redpoll
- Open birch and willow tundra with shrubs and grass understory.
- Riparian thickets and young forest growth.
- Alpine meadows with low shrubs.
Linnet Redpoll
- Coniferous boreal forest, especially spruce.
- Forest openings and edges.
- Muskegs and bogs within boreal forest.
During winter, both species frequent:
- Weedy fields with thistles and brush.
- Stands of birch and alder.
- Backyards and feeders where birch seeds or nyjer seed are available.
So in summary, the key habitat differences are:
- Lesser redpolls nest in open arctic tundra habitats.
- Linnet redpolls nest in coniferous boreal forest.
- In winter, they use similar open habitats.
Physical Features
Lesser and linnet redpolls show subtle but consistent physical differences:
| Feature | Lesser Redpoll | Linnet Redpoll |
|---|---|---|
| Size | Smaller | Larger |
| Length | 4.3-4.7 in (11-12 cm) | 4.7-5.1 in (12-13 cm) |
| Wingspan | 7.5-8.3 in (19-21 cm) | 8.3-8.7 in (21-22 cm) |
| Bill | Small and fine | Longer and stouter |
| Back | Pale brown | Rufous tinge |
| Underparts | Less streaking overall | More streaking overall |
| Flanks | Faint streaks | Heavier streaks |
| Undertail Coverts | Little to no streaking | Moderate to heavy streaking |
In summary, linnet redpolls tend to be larger with a stouter bill, ruddier back, and more streaking on the underparts. But there is much variation and overlap in these features. Experienced birders look for a combination of small size, small bill, pale back, and lack of streaking to identify a lesser redpoll.
Vocalizations
The songs and calls of lesser and linnet redpolls differ consistently:
Lesser Redpoll
- Song is a hurried series of trills and twitters, higher-pitched and grating.
- Call is a very high, thin “sii” or “sssi”.
Linnet Redpoll
- Song is lower-pitched and more musical, interspersed with buzzes and warbled notes.
- Call note is a low, hssh-teeee or te-te-te.
Audio recordings provide the most reliable way to identify these species by voice. In general, linnet redpolls sound deeper and huskier while lesser redpolls are brighter and higher-pitched.
Behavioral Differences
Lesser and linnet redpolls share general behaviors typical of finches:
- Forage in flocks, sometimes mixed together or with other finch species.
- Feed primarily on small seeds from herbaceous plants, shrubs, trees.
- Frequent bird feeders in winter for small seeds.
- Nest in shrubs or small conifers.
However, some differences in feeding behavior parallel their habitat preferences:
- Lesser redpolls feed more on catkins and buds of birch, alder, and willow typical of the tundra zone.
- Linnet redpolls feed more on conifer seeds typical of the boreal forest.
Lesser redpolls also appear more gregarious than linnet redpolls. They form larger flocks and associate more readily with other finch species like common redpolls and siskins.
Breeding and Nesting
The breeding ecology of lesser and linnet redpolls is adapted to their high-latitude ranges:
Lesser Redpoll
- Nest timing is linked to snowmelt in late May to June.
- Open cup nests built low in shrubs, conifers, or on ground.
- Clutch size averages around 5 eggs.
- May raise 2-3 broods per season.
- Feed nestlings insects like midges early in season.
Linnet Redpoll
- Nest from late April to early June.
- Cup nests in conifers slightly higher than lesser redpolls.
- Clutch size around 4-6 eggs.
- Raise 1-2 broods per season.
- Nestlings fed more seeds and fewer insects.
So in summary, lesser redpolls breed slightly later following snowmelt, have bigger clutches, and feed more insects to young compared to linnet redpolls. Both species are adaptable and opportunistic breeders to take advantage of short northern summers.
Conservation Status
Both lesser and linnet redpolls have large populations and expansive ranges across Eurasia and North America. They are classified as Least Concern by the IUCN due to their numbers and lack of major threats.
Estimated global population sizes are:
- Lesser redpoll – 60 million
- Linnet redpoll – 19 million
Population trends appear stable overall. Numbers fluctuate from year to year, especially in winter. Threats like habitat loss and disease could become issues with climate change and expanding human activity in the Arctic. Continued monitoring is recommended to detect any concerning declines.
Relationship Between the Species
Lesser and linnet redpolls represent a classic case of “speciation in action” among closely related bird species:
- They likely diverged in isolation during past ice ages when ranges were fragmented.
- Slight differences evolved in size, plumage, voice, and habitat adaptations.
- Their breeding ranges now reconnect across the boreal zone but differences are maintained.
- They appear reproductively compatible and interbreed occasionally where ranges overlap.
Ongoing gene flow prevents full separation, blurring the lines between distinct “species” versus “subspecies”. More research is needed to understand the evolutionary forces at play.
Similar patterns occur in other northern finch pairs like common/hoary redpolls and pine/Cassia’s siskins. Harsh polar environments and cyclical ice ages spur rapid evolution.
Conclusion
In summary, the key differences between lesser and linnet redpolls include:
- Slight differences in size, plumage, and voice
- Lesser redpolls breed further north in tundra, linnet in boreal forest
- Lesser redpolls have paler plumage overall with less streaking
- Linnet redpolls are more restricted to boreal habitats year-round
- Their songs and calls are consistently distinctive
Their classification as separate species is debated, but evidence is accumulating in favor of this split. More research into their genetics, vocalizations, and breeding biology will shed light on their evolutionary relationship and taxonomic status. Careful study is required to distinguish between lesser and linnet redpolls in the field due to frequent overlap in their plumage characteristics. Paying attention to vocalizations, subtle plumage clues, size and bill differences, and geographic range is the best approach for confident identification.
