The rose-breasted grosbeak is a distinctive bird, most easily detected in May, when males often sing from high in the tree tops. The spring appearance usually occurs between the 06 and 22 May, occasionally a little later. The late spring of 2014 falls in this generalization: the first of the year, a singing male, was seen high in a tree on the edge of the esker just west of Campbellford, on Victoria Day, 19 May. The rose-breasted grosbeak is most commonly encountered as individuals and in pairs. Departure dates are less well-constrained, but only two sightings are as late as 20 August to 02 September.
In contrast, the pine grosbeak is a winter species, a visitor more often found in small flocks. Four were seen on 12 November 2007, and eleven birds some six weeks later, on 24 December of that year. One or more small flocks may have spent at least three of the intervening weeks in town, feeding on berries in gardens, and even getting tipsy from the fermenting juices and flying into windows (Doug Seymour, pers.commun., 2007). One pine grosbeak was noted on 25 February 2005, and two days later a flock of 18 birds was sighted. On the 17 February 2013, a female pine grosbeak was seen at a heated bird bath in a Campbellford garden.
The rose-breasted grosbeak is widespread in southern Ontario: it is also sighted in townships to the east and south, and along the north shores of lakes Ontario and Erie at at Presqu'ile, Pelee and especially Rondeau parks. The pine grosbeak in contrast is more often seen to the north and west in Ontario, e.g., in the Thunder Bay region.
A third species is the striking evening grosbeak (Hesperiphona vespertina), which we have seen to the north in May in a west to east band from northern Michigan to the Algoma region to Mattawa in the upper Ottawa valley. We have yet to see an evening grosbeak in Trent Hills, but they are noted to the south, along the shore of Lake Ontario, as at Presqu'ile park.
In summary, it seems that the two visiting species are quite distinct in their times of residence in Seymour township, with no overlap: we see uncommon flocks of pine grosbeaks in the cold winter months and enjoy occasional glimpses and serenades by their rose-breasted cousin in spring and summer, most often in May.
At Presqu'ile provincial park, roughly 40 km to the south, the rose-breasted grosbeak is a common May migrant and a rare breeding summer resident. Migrants return in mid-August and are gone in the first week of October (LaForest, 1993, pp.342,379), The pine grosbeak is an irregular winter visitor from early November to early March; an observation very similar to the pattern in Seymour township in the past 15 years. As with other occasional visitors winter irruptions can involve significant flocks, up to 125 birds (ibid., p.379).
Similar patterns apply also in Peterborough county, to the northwest (Sadler, 1983, pp.144,161). The rose-breasted grosbeak is a common summer resident, in season circa 01 May to 04 September. The pine grosbeak is not known to nest in the county, but is an erratic winter visitor, from 26 October to 16 April. The rose-breasted grosbeak increased in numbers in much of Ontario, 1967-1983, and occurs northwards as far as the extent of abundant deciduous tree cover. The pine grosbeak, one of the "winter finches", prefers open coniferous forests for breeding, further to the north (Cadman et al., 1987, pp.432-433, 488-489). Furthermore, the second edition of the provincial breeding bird atlas affirms the 20th century expansion of the rose-breasted grosbeak in Ontario, Quebec and New York state, and notes that the pine grosbeak, seen by most birders in its winter irruptions, is secretive and hard to study at the nest sites in northern Ontario (Cadman et al., 2007, pp.580-581, 608-609).
Cadman,MD, Eagles,PFJ and Helleiner,FM (1987) Atlas of the Breeding Birds of Ontario. Federation of Ontario Naturalists and Long Point Bird Observatory, published by University of Waterloo Press, 617pp.
Cadman,MD, Sutherland,DA, Beck,GG, Lepage,D and Couturier,AR (editors) (2007) Atlas of the Breeding Birds of Ontario, 2001-2005. Bird Studies Canada, Environment Canada, Ontario Field Ornithologists, Ontario Ministry of Natural Resources, and Ontario Nature, 706pp.
LaForest,SM (1993) Birds of Presqu'ile Provincial Park. Friends of Presqu'ile Park / Ontario Ministry of Natural Resources, 436pp.
Sadler,D (1983) Our Heritage of Birds: Peterborough County in the Kawarthas. Peterborough Field Naturalists / Orchid Press, Peterborough, ON, 192pp.