VU
Evening Grosbeak Hesperiphona vespertina



Justification

Justification of Red List Category
Following a large increase in range and population size prior to 1920, recent surveys suggest a steep decline both in abundance and in locations throughout the range. The species is therefore listed as Vulnerable.

Population justification
The population size has been estimated at 3.4 million mature individuals (Rosenberg et al. 2016). This equates to 5.1 million individuals in total.

Trend justification
This species has undergone a large and statistically significant decline over the last 40 years in North America (77.7% decline over 40 years [Butcher and Niven 2007]). More recent estimates suggest an even steeper rate of decline (94% between 1970 and 2014 [Rosenberg et al. 2016]). The species may have disappeared from 50% of recorded sites between 1988 and 2006, and where the species remained, abundance dropped by 27% (Bonter and Harvey 2008). Taken from long-term trends (1966-2017), data from the Christmas Bird Count suggest an annual decline of 3.47% (1.43-6.23% annual decline) in this species (T. Meehan in litt. 2018). This would equate to a reduction of 44.16% (21.13-65.42%) over three generations, and trends appear to be ongoing, as Breeding Bird Survey data from between 2005 and 2015 gives an annual decline of 2.9% (0.09-5.45% per year) (Sauer et al. 2017), roughly equating to a decline of 38.5% (1.5-60.3%) over three generations. Therefore, declines are placed here in the range 30-49% over three generations.

Distribution and population

The species is found in continental North America, where it occurs from southern Canada through large parts of the U.S.A. to western and southern Mexico. In the 19th century, the species started expanding its range from western U.S.A. northward into Canada and eastward to the Atlantic coast. This range expansion culminated around 1920. It was accompanied by an increase in population size and might be attributable to the spread to Box Elder Acer negundo as an ornamental tree in eastern cities and to peaks in insect abundance, both providing a food source to the species (Gillihan and Byers 2001).

Ecology

The Evening Grosbeak occurs in northern conifer or mixed forests, but also occupies secondary growth and sometimes urban parks and orchards (Gillihan and Byers 2001). Individuals in the northern part of the range migrate southward as a response to food scarcity and return to the breeding grounds by mid-May (Gillihan and Byers 2001). It mainly feeds on invertebrates (spruce budworms and other larvae), but also on small fruits and seeds (Gillihan and Byers 2001).

Threats

The species has been undergoing rapid declines in the last decades (Bonter and Harvey 2008, Ralston et al. 2015, COSEWIC 2016, Rosenberg et al. 2016, Sauer et al. 2017). However, the reasons for decline are not yet identified. It has been suggested that the alteration of habitats, diseases, collisions with windows and the control of its insect prey (e.g. spruce budworm) are potential contributing factors (Gillihan and Byers 2001, Bonter and Harvey 2008).

Conservation actions

Conservation Actions Underway Listed as Special Concern in Canada (COSEWIC 2016).

Conservation Actions Proposed Monitor the population trend and assess potential threats and their impacts on the population size and distribution range.

Identification

c.16-18 cm. A large, robust finch with a massive green-yellow bill. Male has a brown-black head with a black crown, yellow forehead, brown nape, yellow scapulars and rump; brown-yellow breast and underparts; black tail-coverts; wings and tail black with white patch on inner coverts. Female has a more greyer head and upperparts, with black stripe and yellow wash on the sides of the neck; black tail-coverts with white spots; wings and tail black with grey patch on inner coverts. Similar spp Easily distinguishable for its massive beak and distinctive plumage coloring. Voice Song an erratic series of warbling notes and short whistles; sharp, loud call.

Acknowledgements

Text account compilers
Ekstrom, J., Westrip, J., Hermes, C., Butchart, S.

Contributors
Meehan, T.


Recommended citation
BirdLife International (2019) Species factsheet: Hesperiphona vespertina. Downloaded from http://www.birdlife.org on 21/08/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 21/08/2019.