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Cape May Red Crossbills

Authors Michael O’Brien & Tom Johnson:

New Jersey’s Cape May peninsula has been well watched by birders for over a century, making it an excellent place to attain insight into the long-term ebb and flow of irruptive species like Red Crossbill (Loxia curvirostra). As Red Crossbills have never been known to nest in Cape May County, their presence here in modern times appears to be strongly correlated with widespread regional irruption events. However, reports of nesting in the pine barrens of nearby Ocean and Burlington counties (Walsh et al. 1999) suggests that breeding in Cape May County is something to watch for.

Apparently very rare in the early part of the 20th century, Stone (1937) noted but one record of Red Crossbill for Cape May County, a bird found dead on 4 March 1923. Through the middle of the 20th century, records were few until a major irruption occurred into New Jersey in the fall/winter of 1952/53 (Walsh et al. 1999), as well as elsewhere in the Northeast in 1963/64 and 1965/66 (CBC data). Widespread irruptions reached Cape May in 1969/70, 1973/74, 1975/76, and 1981/82 (Sibley 1997, Walsh et al. 1999). Then, after a gap of more than a decade with only a handful of records, another flurry of irruptions occurred into Cape May in 1997/98, 1999/00, 2001/02, 2007/08, 2012/13, 2016/17, 2018/19, and 2020/21 (Sibley 1997, eBird). The largest of these irruptions were in 1973/74, 1975/76, 2012/13, and 2020/21, when high counts numbered in the low hundreds (Sibley 1997, eBird). When these irruptions occur, eBird data shows that the first birds typically appear in Cape May in late October/early November, with peak counts around the end of November. Numbers then trail off through December and January, with only occasional records through early April, and a very few records into mid-May. Additionally, there are single records in June 2013 and July 2019.

Figure 1. eBird bar chart showing Red Crossbill occurrence in Cape May County, New Jersey.

When Red Crossbills do occur in Cape May County, they are regularly seen in active migration, commuting between feeding sites, and feeding in conifers. Many records here are of individuals or flocks flying past migration watch points in morning flight, though it is clear that during peak movements, birds pass by through most of the daylight hours, not just during the heavily watched hours immediately after dawn. When crossbills settle in and feed for extended periods, it can be difficult to keep track of which flying flocks are actively migrating and which are simply commuting between feeding sites. However, in some cases such as the large 2012/13 and 2020/21 irruptions, flocks of crossbills were regularly seen departing Cape May Point and flying south or west over Delaware Bay, presumably on to coastal points south along the Delmarva Peninsula.

In the 1990s, after Jeff Groth published his landmark manuscript on the Red Crossbill complex (Groth 1993), observers began to scrutinize Red Crossbills more closely, and in particular, pay close attention to their flight calls. From audio recordings, we have good documentation on which Red Crossbill “types” occurred during irruptions from 1997 onward. In total, five different types have been recorded, including Types 1, 2, 3, 4, and 10. Of these, Type 10 is the most frequent, being the dominant type recorded in all irruptions except 2012/13, when Type 3 was dominant.

Though Red Crossbills do forage on the seeds of native pine species like Pitch Pine (Pinus rigida), Loblolly Pine (Pinus taeda), and Virginia Pine (Pinus virginiana) in the northern half of Cape May County (and elsewhere in the New Jersey Pine Barrens), most local feeding observations come from the strips of introduced Japanese Black Pine (Pinus thunbergii) that line the dunes of Cape May Point and some streets on the Atlantic-side barrier islands. Some of this observed dynamic is surely due to the observer bias of the many birders who specifically canvass Cape May Point during irruptive events (and largely ignore the native pine forests farther north), but the geography of the Point itself also obviously concentrates irrupting crossbills. The mid-sized, hard cones of Japanese Black Pines often hold seeds through the winter in Cape May, and they provide a locally abundant food source for irruptive Red Crossbills. In recent years, as some non-native Japanese Black Pines have died off, crossbills have been seen feeding on seeds from the dead, open pinecones in addition to tightly closed cones. During the past two decades, Types 2, 3, and 10 have been observed feeding on Japanese Black Pine seeds in Cape May Point.

A Type 10 Red Crossbill feeds on a Japanese Black Pine Cone in the dunes of Cape May Point. Video by Tom Johnson.

Below is a summary of the local occurrence of each of the five Red Crossbill call types that have been documented in Cape May.

Type 1 Red Crossbills give abrupt, downward-inflected chewp-chewp flight calls. They are most commonly encountered in the Southern Appalachians and parts of the Northeast, but can occasionally be found in small numbers in coastal areas of western North America. Type 1 Red Crossbills were recorded in Cape May during two irruptions with singles on 13 Dec 2012, 2 Jan 2013, and 14 Nov 2020, plus 2 on 7 Dec 2020. Another bird on 24 July 2018 was very likely Type 1 as well, but no audio was obtained for confirmation. Despite the proximity of Cape May to the core Appalachian Mountain breeding grounds of Type 1, this call type is quite rare on the Atlantic Coastal Plain south of New England, and these records are apparently the only ones for New Jersey.

Type 1, perched, then flying, 13 Dec 2012 (MOB):

https://macaulaylibrary.org/asset/300643321

Figure 2. Type 2 Red Crossbill at Cape May Point, NJ. 3 Dec 2012. This is the largest-billed crossbill type we see in Cape May. Photo by Michael O’Brien.

Type 2 Red Crossbills give softer, lower pitched calls than Type 1, sounding like a downward-inflected chew-chew. Type 2s are most common in the Mountain West, including the Rockies, Sierras and Cascades, but occur somewhere in the East in small numbers every year. Type 2 Red Crossbills were recorded in Cape May during five irruptions. Seasonal maxima are 3 on 11-18 Dec 1997, 4 on 14 Dec 2007, 4 on 3 Dec 2012, 3 on 19 Nov 2018, and 7 on 18 Nov 2020. Most of these records are of the “unkinked” (eastern) type, however, a few are of the “kinked” (western) type, including birds on 3 Dec 2012, 19 Nov 2018, and 22 Nov 2020. Still others seem ambiguous, with only a hint of a kink. Though Type 2 birds have been seen flocking with Type 3 and Type 10, multiple observations in Cape May have included Type 2 crossbills segregated away from other crossbill types.

Type 2 (unkinked), single flyover, 13 Dec 1997 (MOB):

https://macaulaylibrary.org/asset/287461431

Type 2 (kinked), single flyover, 3 Dec 2012 (MOB):

https://macaulaylibrary.org/asset/301242451

Type 2 (unkinked), two birds feeding, 19 Nov 2018 (TBJ):

https://macaulaylibrary.org/asset/124297611

Figure 3. Type 3 Red Crossbill at Cape May Point feeding on Japanese Black Pine. 13 Jan 2013. This is the smallest-billed crossbill type we see in Cape May. Photo by Michael O’Brien.

Type 3 Red Crossbills give rather high, harsh or squeaky kyip-kyip flight calls. This type is most commonly found from the Pacific Northwest to Alaska, but also frequently irrupts into the East. Type 3 Red Crossbills were recorded in Cape May during six irruptions. Seasonal maxima are 9 on 20 Dec 1997, 6 on 12 Dec 1999, 1 on 21 Dec 2010, 166 on 16 Nov 2012, 2 on 17 Nov 2018, and 5 on 20 Dec 2020. They have been found locally in flocks with Type 2 and Type 10 crossbills, though during the large 2012/13 irruption, Type 3 was the dominant call type in Cape May flocks. Although numerous at times, we have seen very little variation in this call type in Cape May; a notable exception is one individual on 1 Dec 2012, which has a distinct kink in the descending slope of the call.

Type 3 perched, 1 Jan 1998 (MOB):

https://macaulaylibrary.org/asset/302404441

Type 3 perched, 4 Jan 2021 (TBJ):

https://macaulaylibrary.org/asset/294471751

Type 3, large flock perched, then flying out over Delaware Bay, 1 Dec 2012 (MOB):

https://macaulaylibrary.org/asset/302411231

Type 3, odd variation with kinked downslope, 1 Dec 2012 (MOB):

https://macaulaylibrary.org/asset/302353481

Type 4 Red Crossbills are quite distinctive sounding, and give bouncy, V-shaped pwit-pwit flight calls. They are most common in the Pacific Northwest and are rarely encountered east of the western Great Lakes. Type 4 Red Crossbills were recorded in Cape May during one irruption, with singles on 11 and 15 Nov 2020. One was mixed with a flock of Type 10 crossbills that departed Cape May Point to the south (TBJ) and the other was detected by itself in morning flight over West Cape May (MOB). These are apparently the first documented records for New Jersey (published records of “Type 4” from Cape May before 2010 actually refer to Type 10 – Type 10 simply hadn’t been described yet and those calls were lumped in with Type 4 calls).

Type 4, single bird among flock of Type 10s, giving V-shaped flight calls; clearest examples are four calls between .04-.07s, 11 Nov 2020 (TBJ): 

https://macaulaylibrary.org/asset/279155111

Type 4, faint calls from single flyover, 15 Nov 2020 (MOB):

https://macaulaylibrary.org/asset/302495371

Figure 4. Type 10 Red Crossbill at Cape May Point. 6 Dec 2018. It is common to see Red Crossbills feeding on seeds from dead or dying Japanese Black Pines in Cape May. Photo by Tom B. Johnson.

Of the crossbills showing up in Cape May, Type 10 Red Crossbills show the most variable flight calls, sorting into “upslurred” and “overslurred” groups. Upslurred Type 10s give clean rising notes, recalling the whit of a Least Flycatcher. Birds of this call type are most common along the outer Pacific Coast from northern California to Vancouver Island, British Columbia. However, they can also be found in the East some years. Overslurred Type 10s give a harder, squeakier kip-kip with a strong downward inflection at the end, looking like an upside down V; the strength of the downward portion seems to vary quite a bit, and is sometimes the dominant portion of the call. This overslurred Type 10 appears to be the most common call type found in the Maritimes and Northeastern United States. Type 10 Red Crossbills have been recorded in Cape May during nine irruptions. Seasonal maxima are 16 on 16 Nov 1997, 16 on 16 Dec 1999, 19 on 11 Nov 2001, 17 on 21 Dec 2007, 15 on 3 Dec 2012, 9 on 22 Nov 2016, 5 on 17 Nov 2018, 1 on 10 Nov 2019, and 256 on 22 Nov 2020. Birds recorded during irruptions before 2012 were all of the upslurred type. Birds from after 2012 were all of the overslurred type. In 2012, we saw and heard both upslurred and overslurred Type 10 varieties, as well as some that looked intermediate. As a side note – since Type 10 was formally described quite recently, in 2010, early published records of “Type 4 Red Crossbills” from Cape May refer instead to Type 10.

Type 10, typical upslurred type, single flyover, 3 Dec 2012 (MOB):

https://macaulaylibrary.org/asset/301246331

Type 10, typical overslurred type, single perched bird, 26 Nov 2020 (TBJ):

https://macaulaylibrary.org/asset/283162381

Type 10, both upslurred and overslurred types, and intermediates, flyover group, 3 Dec 2012 (MOB)

https://macaulaylibrary.org/asset/302447281

Type 10 (overslurred), song and call from perched birds, 11 Dec 2020 (TBJ): 

https://macaulaylibrary.org/asset/287147731

Figure 5. Type 10 Red Crossbill hanging from Japanese Black Pine cone at Cape May Point. 31 Dec 2007. Photo by Michael O’Brien.

Type 10 (overslurred), feeding birds giving soft calls and cone crunching, 2 Jan 2021 (TBJ):

https://macaulaylibrary.org/asset/293782171

Type 10 (overslurred), large flock in flight, 2 Jan 2021 (TBJ):

https://macaulaylibrary.org/asset/293780131

Mixed flyover flock of types 2 (unkinked), 3, and 10 (upslurred), 11 Dec 1997 (MOB):

https://macaulaylibrary.org/asset/303555641

Mixed flyover flock of types 2 (unkinked) & 10 (overslurred), 20 Nov 2018 (TBJ)

20 Nov 2018 (TBJ): https://macaulaylibrary.org/asset/124453051

Mixed flyover flock, mainly Type 10s (overslurred) with at least one Type 3, 21 Dec 2020 (TBJ):

https://macaulaylibrary.org/asset/124453051

Mixed flock, mainly Type 3 but at least one Type 10 (upslurred), giving various calls while perched before taking off, 1 Dec 2012 (MOB):

https://macaulaylibrary.org/asset/73594051

Acknowledgments:

We’d like to thank the Cape May birding community for helping to keep track of irruptive crossbills. In particular, we wanted to highlight the following individuals who have contributed additional Red Crossbill recordings from Cape May County to the large archive at the Macaulay Library (192 recordings at the time of publication): Tom Auer, Chris Daly, Sam Galick, Alex Lamoreaux, Jerald Reb, and Tom Reed.

Literature cited:

Groth, Jeffrey G. 1993. Evolutionary differentiation in morphology, vocalizations, and allozymes among nomadic sibling species in the Red Crossbill (Loxia curvirostra) complex. University of California Publications in Zoology 127:1-143.

Sibley, David S. 1997. The Birds of Cape May, 2nd Edition. New Jersey Audubon’s Cape May Bird Observatory, Cape May Court House.

Stone, Witmer. 1937. Bird Studies at Old Cape May: An Ornithology of Coastal New Jersey. Delaware Valley Ornithological Club at the Academy of Natural Sciences, Philadelphia.

Walsh, Joan, Vince Elia, Rich Kane, and Thomas Halliwell. 1999. Birds of New Jersey. New Jersey Audubon Society, Bernardsville.

Cover Photo Michael O’Brien. Type 10 Red Crossbill at Cape May Point 31 Dec 2007. Bios for both Michael O’Brien and Tom Johnson can be found here:  https://ventbird.com/our-team/MichaelOBrien/51 and https://fieldguides.com/guides/tom-johnson/

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For more on Red Crossbills, please read below:

Type 10 Red Crossbill in flight at Cape May Point. 27 Nov 2020. Photo by Tom B. Johnson.

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