Evening Grosbeak

Evening Grosbeaks breed in coniferous and mixed forests, and pairs typically form before the birds arrive on the breeding grounds. Courtship is notably quiet — there is no elaborate territorial song. Instead, the male performs a "dance" display: he raises his head and tail, droops and vibrates his wings, and swivels back and forth. In a second display, both members of a pair bow alternately to each other. Males feed females frequently during courtship and throughout incubation.

The mating system is typically monogamous, though polygyny can occur when food is unusually abundant — a flexibility that reflects the species' opportunistic relationship with boom-and-bust food supplies. Males do not defend feeding territories during the breeding season, likely because food sources such as spruce budworm outbreaks are so locally concentrated that defence would be impractical.

Nests are placed high in trees or large shrubs, typically 20–60 feet above ground (occasionally as low as 10 feet or as high as 100 feet). Preferred nest trees include spruce, fir, Douglas-fir, white cedar, paper birch, beech, sugar maple, and willow. The nest is usually positioned on a horizontal branch well out from the trunk, or in a vertical fork. The female does most of the building, constructing a flimsy, saucer-shaped cup of small twigs and roots lined with grasses, fine rootlets, lichens, or pine needles. It measures approximately 5 inches across and 5 inches high, with an inner cup of about 3 inches across and 1 inch deep.

Clutch size is 2–5 eggs, typically 3–4. Eggs are pale blue to blue-green, blotched with brown, grey, or purple, and measure approximately 0.8–1.0 inches long by 0.6–0.7 inches wide.

The female incubates alone for 12–14 days, fed by the male throughout. Nestlings hatch helpless, with eyes closed and dark skin partly covered with white down. Both parents feed the young, which fledge after 13–14 days and continue to be fed by the parents for a further 2–5 days. The species raises 1–2 broods per year. Because nesting takes place high in the canopy and birds are secretive during this period, the breeding biology of Evening Grosbeaks remains relatively poorly studied.

Evening Grosbeaks are relatively long-lived for finches. Typical lifespan in the wild is estimated at 5–10 years, though survival rates vary considerably with food availability, disease pressure, and collision risk. The oldest recorded individual was a male banded in Connecticut in 1959 and recovered in New Brunswick, Canada, in 1974 — a minimum age of 16 years and 3 months. The AnAge longevity database records a maximum of 17 years for the species, which is exceptional for a bird of this size.

For comparison, the closely related Hawfinch — the Evening Grosbeak's Eurasian ecological counterpart — has a recorded maximum longevity of around 12 years, making the grosbeak's 17-year record notably high. The Greenfinch, another Fringillidae member, averages just 2–3 years in the wild.

Key mortality factors include window and vehicle collisions (elevated by the species' road-salt foraging habit), predation, and disease — particularly salmonella, West Nile virus, and House Finch eye disease (Mycoplasmal conjunctivitis), which can spread rapidly through the dense winter flocks that gather at feeders.

Climate-driven changes to food availability, particularly the suppression of spruce budworm outbreaks through aerial spraying, may also affect survival and reproductive success by reducing the protein available to breeding adults and nestlings. Satellite tracking studies are beginning to identify where and when across the annual cycle losses are greatest.

The Evening Grosbeak is listed as Vulnerable on the IUCN Red List (2018), with an estimated global population of approximately 3.4–3.8 million mature individuals. The decline is severe by any measure. The North American Breeding Bird Survey records an estimated 3.1% annual decline between 1966 and 2023, equating to a cumulative loss of around 84% over that period. The Road to Recovery initiative and the Finch Research Network cite a 92% decline since 1970 — making it the steepest declining landbird in the continental United States and Canada. In Canada specifically, long-term BBS data indicate an 82% decline since 1970, while Christmas Bird Count data show an 87% fall over a similar period.

A 2008 Project FeederWatch study found the winter range had contracted sharply: the species was reported at only half the number of sites compared to the late 1980s, and flock sizes had fallen by 27%. From being one of the most common feeder birds across North America in winter, the Evening Grosbeak has become a genuinely scarce visitor across much of its former winter range in under 40 years.

Multiple threats are implicated. Fluctuations in spruce budworm populations — including aerial spraying programmes designed to suppress outbreaks — remove a critical breeding-season food source. Loss and alteration of mature boreal and montane forests through logging and oil sands development reduces available nesting habitat. Climate change is projected to cause balsam fir to retreat from New England, potentially eliminating the species from that region entirely.

Vehicle and window collision mortality is elevated by the species' habit of foraging for road salt. Disease — including salmonella, West Nile virus, and House Finch eye disease — takes an additional toll. The relative contribution of each threat remains difficult to disentangle, and current conservation research is working to identify which parts of the annual cycle are most limiting.

The Evening Grosbeak is protected under the Migratory Birds Convention Act in Canada and the Migratory Bird Treaty Act in the USA. It is listed as a Species of Special Concern by COSEWIC (Canada, 2016) and as an Orange Alert Tipping Point Species in the 2025 State of the Birds report. It is one of four pilot species for the Road to Recovery conservation initiative, which uses satellite and radio tracking to study full annual-cycle movements and identify the limiting factors driving the decline.

Few North American birds have a more complex vocal geography than the Evening Grosbeak. Research by Sewall, Kelsey, and Hahn (2004) identified five distinct flight call types, each geographically restricted to a different population across the continent. These are not subtle regional accents — they are sufficiently different that experienced birders can identify the population origin of a bird from its call alone, and spectrograms show clear structural differences between types.

The Pacific Northwest and northern Rockies are home to Type 1 (brooksi), whose call is a descending "chee-er" — clear, thin, and whistled, starting at a high frequency with a sharp drop. The Sierra Nevada of California holds Type 2 (californicus), the most purely whistled of all five: distinctly higher-pitched and more piercing. Types 2 and 4 share a high-pitched, piercing quality — Type 4 (warreni), from the southern Rockies of Colorado and New Mexico, is essentially huskier and less clear than its Sierra counterpart. Boreal Canada east of the Rockies and the northeastern USA are the territory of Type 3 (vespertina): slightly longer, lower-pitched, and distinctly burry, it is the type most familiar to eastern birders and the basis of most field guide descriptions. At the southern extreme, Type 5 (montana) — found in the Sierra Madre of Mexico north to southeastern Arizona — is the longest and burrriest of all, yet shares the high pitch of Types 2 and 4.

Subsequent work by Aaron Haiman (2009) found that bill morphology also differs among call-type groups, particularly in females. This combination of vocal and morphological divergence is strikingly similar to the situation in Red Crossbills, where call-type populations are now considered potential species. The Cassia Crossbill — formerly Red Crossbill Type 9 — was formally split as a separate species in 2017. Whether one or more Evening Grosbeak call types will eventually receive the same treatment remains an open question, but the evidence is accumulating.

Few relationships between a bird and an insect are as ecologically intertwined as that between the Evening Grosbeak and the spruce budworm (Choristoneura fumiferana). The budworm is the most destructive forest insect in North America, periodically erupting in outbreaks that defoliate millions of hectares of spruce and fir across the boreal forest. For the Evening Grosbeak, these outbreaks are a bonanza: the larvae are protein-rich, locally superabundant, and available precisely when breeding adults and nestlings need high-quality food most.

During the major budworm outbreaks of 1945–1955 and 1968–1988, Evening Grosbeak populations tracked the infestations closely, with large irruptions of birds moving into affected areas. The grosbeaks became so reliably associated with budworm outbreaks that foresters learned to treat their sudden appearance as an early warning of an infestation — a biological indicator that preceded formal survey data. Banding stations in Pennsylvania recorded over 4,000 Evening Grosbeaks in the 1970s; by the 2000s, the same stations were recording near-zero.

The relationship has a darker side. Aerial spraying programmes designed to suppress budworm outbreaks remove a critical food source at the exact moment when grosbeaks need it most, and the collapse of budworm populations through chemical control may be one of the factors driving the grosbeak's long-term decline. The relative contribution of this threat compared to habitat loss, collision mortality, and disease remains difficult to disentangle.