Dramatic Declines of Evening Grosbeak Numbers at a Spring Migration Stop-Over Site

Robinson, W. Douglas; Greer, Jessica; Masseloux, Juliana; Hallman, Tyler A.; Curtis, Jenna R.

doi:10.3390/d14060496

Cited by 2 publications

(4 citation statements)

References 35 publications

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“…The rapidly increasing number of recordings collected by community scientists and archived in public databases such as the Macaulay Library (eBird) and xeno-canto.org (Figure 5), provides an unparalleled opportunity to monitor the movements and map the geographic ranges of Evening Grosbeaks. Type 1 grosbeaks, in particular, appear to engage in fairly consistent spring migration patterns, appearing in Pacific Northwestern woodlands each spring (Robinson et al, 2022). However, dynamism exists in their patterns of migratory movement and selection of breeding range, neither of which have been well quantified.…”

Section: Discussionmentioning

confidence: 99%

“…The campus of Oregon State University in Corvallis, Oregon (44.56570, -123.27890), is a well-known spring migratory stopover site where Evening Grosbeaks forage on tree seeds for several weeks before continuing their migration to breeding sites (Robinson et al, 2022). In the 1970s, 150,000 to 250,000 birds gathered on campus to consume elm seeds but in recent decades the numbers have declined to 10,000 or fewer birds.…”

Section: Study Areamentioning

confidence: 99%

“…As grosbeaks are social and noisy birds, we listened for their calls to locate them. Once discovered, we counted them (see Robinson et al, 2022 for further details) and recorded them.…”

Section: Study Areamentioning

confidence: 99%

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Flight calls and trills of Evening Grosbeaks can be used to map movements and ranges of call types 1 and 2

Robinson,

Nanau,

Kirsch

et al. 2024

Front. Bird Sci.

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Evening Grosbeak (Coccothraustes vespertinus) is a species of North American Fringillid finch thought to be one of the fastest declining songbirds across North America. It has been divided into five groups, potentially distinct lineages, based in part on structure of their flight calls. The primary flight calls of each type exhibit structural variation that has not been described and the degree to which that variation might lead to identification errors has not been quantified. We describe the variation in call structure of type 1 Evening Grosbeaks recorded at a spring migratory stopover site (Corvallis, Oregon) and nearby areas in the Pacific Northwest, USA. We recorded grosbeaks weekly from April through early June 2023. We reviewed more than 10,000 recorded call notes to characterize the variety of calls and their configurations. We found a high diversity of call notes including at least 11 recurring readily identifiable variants of the primary flight calls, all of which were attributed to individuals thought to be type 1 birds. Geographically, the nearest neighbors of type 1 Evening Grosbeaks are type 2s, which have uncommonly been recorded in our study area but whose breeding range appears to overlap that of type 1 in southern Oregon. We quantified recordings of type 2 flight calls and compared them with type 1 flight calls, finding that linear discriminant function analyses correctly identified >95% of recordings to type. Inclusion of a metric of asymmetry in call shape improved correct classification to 98.5%. We also found that the other dominant calls given by both types, buzzy trills, could be identified correctly to type with a high level of confidence. The sufficiently different characteristics of flight calls and trills indicate that types 1 and 2 are identifiable spectrographically in most cases, providing confidence that the geographic distribution and migratory movements of call-type populations, despite being essentially identical in plumage, can be documented effectively by characteristics of call notes.

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Section: Discussionmentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

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Flight calls and trills of Evening Grosbeaks can be used to map movements and ranges of call types 1 and 2

Robinson,

Nanau,

Kirsch

et al. 2024

Front. Bird Sci.

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“…Like other nomadic finches, Evening Grosbeaks present a challenge to mapping spatial distributions of subspecies that are essentially impossible to identify visually. Variable movements and changes in breeding density from year to year (Gillihan and Byers, 2001;Robinson et al, 2022; this study) prevent clear definition of ranges and abundances, and this irregular distribution combined with the cryptic habits of birds in the breeding season (Bekoff et al, 1989) makes it difficult to study breeding distribution and behaviors. This challenge has prevented clear geographic definition of the ranges and overlap zones of the subspecies and call types of Evening Grosbeak, a critical step for assessing taxonomic status of these groups (James, 2010).…”

Section: Introductionmentioning

confidence: 93%

Sympatric breeding occurrence of two call types of Evening Grosbeak in Western Wyoming

Duman,

Hahn

2024

Front. Bird Sci.

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The Evening Grosbeak (Coccothraustes vesperitinus Cooper, 1825) is a species with multiple vocally distinct recognized groups known as call types. The range boundaries and degrees of overlap between these groups remain an area of continuing research. We report sympatric breeding occurrence of Evening Grosbeaks of call type 1 and call type 4 in the Jackson Hole area of Wyoming, and we show that these two call types have been overlapping in this region for at least 24 years. We also note a major increase in the local abundance of Evening Grosbeaks in 2023 compared to past years. These findings suggest that the range boundary between these two call types is relatively consistent at this short time scale, but it may fluctuate somewhat given changes in the proportions of the two types over this period. We detected both call types continuously through the 2023 breeding period in the Jackson Hole area, and we had breeding season detections of both types in the area in 2000, 2005, 2006, 2007, 2008, 2010, and 2012. In 2023, a majority were the Pacific Northwest-centered type 1 while roughly a quarter were type 4 which is known from the Central Rockies. In 2023, we generally saw type 4 individuals alongside type 1 individuals, and both call types tended to cluster in the same areas though type 1 birds were frequently detected without any type 4s nearby. We most frequently encountered both types in Douglas Fir (Pseudotsuga menziesii Mirb. Franco) or Subalpine Fir (Abies lasiocarpa (Hook.) Nutt.) dominated forests through the June–July breeding season, and both were abundant in areas with Chokecherry (Prunus virginiana L.) or Serviceberry (Amelanchier alnifolia (Nutt.) Nutt. Ex M.Roem.) after the breeding season. Despite considerable survey effort, we could not detect either type north of Moran, WY. Describing this close overlap of call types with uncertain taxonomic status paves the way for further research investigating the potential for ecological and genetic isolation of the two groups in areas where mixed parentage is most possible.

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Dramatic Declines of Evening Grosbeak Numbers at a Spring Migration Stop-Over Site

Cited by 2 publications

References 35 publications

Flight calls and trills of Evening Grosbeaks can be used to map movements and ranges of call types 1 and 2

Flight calls and trills of Evening Grosbeaks can be used to map movements and ranges of call types 1 and 2

Sympatric breeding occurrence of two call types of Evening Grosbeak in Western Wyoming

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