Category Archives: Ornithology

Concepts – Relative vs. Absolute Rarities

Brant

A relatively rare but still exciting Brant at Montrose Point in Chicago, January 2021. (click to see the larger version)

Birders think a lot about rare birds. More than think about — we obsess over them, drive thousands of miles to chase them, and dream about finding them. But what is a rarity? There are a couple of ways to think about this. Most of the rare birds we see are only regionally unusual, that is, they are common someplace within their range but uncommon outside it. The Brant that showed up at Montrose in early January is a good example of this concept. The world population is in the hundreds of thousands, and they’re common on their wintering grounds from New Jersey to Massachusets on the East Coast. Illinois is outside of their main range and migration route, so it’s a big deal here; when one shows up it generates a lot of excitement in the birding community. Brant is rare enough in Illinois to be on the review list of birds requiring documentation, and Montrose has four or so previous records. Relative rareness doesn’t just include birds outside their normal range, it also includes birds outside of their normal timeframe. A Bay-breasted Warbler in Chicago in December is an example.

The other kind of rarity are birds whose entire population is low. The world population of Kirtland’s Warbler in 2020, for example, was a little under 5,000 birds. That’s not a lot. By comparison, the seating capacity of the bleachers at Wrigley Field is about 5,000. Such small populations are vulnerable to all sorts of disturbances. This class has a handful of species, most of which are on the Endangered Species List. Of these, a few have been recorded in Illinois, including Kirtland’s Warbler, and recent records of Whooping Crane and Red-cockaded Woodpecker.

2020 Winter Finches

Purple Finch

Purple Finch, one of the winter finches (click to see the larger version)

Winter Finch – A collective term that refers to Arctic, subarctic, and boreal forest breeding members of the family Fringillidae. This includes redpolls, Pine Siskin, crossbills, Pine and Evening Grosbeaks, and Purple Finch.

This continues to be an excellent fall for winter finches in the Midwest. Common Redpolls, Pine Siskins, and Purple Finches are being seen almost daily at Montrose. Even more exciting were reports of two of the rarer winter finches. On November 3, I found 10 White-winged Crossbills in a spruce tree near the Park Bait Shop (at the corner of W. Montrose Avenue and W. Montrose Harbor Drive), and several observers saw an Evening Grosbeak on November 5. According to eBird, the last White-winged Crossbills from Montrose were in 2012. The last Evening Grosbeak record was about 20 years ago. The rest of the fall should see more of these birds. The Montrose Map page has an interactive map that shows the road system at Montrose.

How to Look for Winter Finches at Montrose

There are a couple of ways to look for winter finches at Montrose. We don’t have a lot of finch habitat but we have some. The pine and spruce trees south of the main entrance of the Sanctuary on W. Montrose Harbor Drive have cones that could attract crossbills. The hawthorns on the service road to the beach house are laden with berries. We’ve been seeing Purple Finches in these hawthorns and they could attract Pine and Evening Grosbeaks. The pine and spruce trees next to the Park Bait Shop don’t have many cones but could attract crossbills and are easy check. Redpolls like weedy areas such as the native planting areas at the south and east end of the Point and north of the Marovitz Golf Course.