The interesting case of the Ipswich Sparrow

The Savannah Sparrow has been recorded , to the best of my knowledge, seven times in the WP: three records in the UK and three in the Azores, plus the very recent one in Poland (June 2020). All the records involve ‘classic’ Savannah Sparrows except the first one, which was asigned to the princeps subspecies, a taxon usually known as Ipswich Sparrow in North America (read the full account about this amazing sighting here). The Ipswich Sparrow is a distinct form that exclusively breeds on Sable Island (Nova Scotia, Canada), a small island of peculiar shape (42 km long but only 1km at its widest point!) situated 175km off the Canadian coast. This taxon is known to overwinter along the Atlantic coast, but with most records concentrated on the stretch from Delaware to New England – and, indeed, it took its name from the city of Ipswich in Massachusetts, where some of the first individuals were collected.

Since most studies try to deal with the taxonomy of the Savannah Sparrow complex as a whole (one of the thorniest and most challenging complexes in North America, with up to seventeen subspecies and perhaps several splits involved), I feel that the distinctiveness and interesting case of the Ipswich Sparrow has gone largely unknown to most European birders, except perhaps for those who have seen one. I will only explain a few relevent aspects about Ipswich Sparrow below, but for a comprehensive review of its status and differences from Savannah please read this detailed paper.

Ipswich Sparrow. October 2016, Massachusetts, USA. Note dull sandy plumage, indistinct head patterm and bulky structure compared to classic Savannah Sparrow - all adding for a more Old World bunting general appearence rather than a Nearctic Sparrow.

Separation of Savannah and Ipswich Sparrows

Ipswich Sparrow consistently diverges from the continental subspecies’ of Savannah in pretty much every aspect you can think of. Ecologically, in addition to the isolated distributions, Ipwich Sparrows are short-distance migrants that spend the winter further north than any other subspecies. They return to the breeding grounds earlier (mid-April) than Savannah Sparrows from the mainland. They rarely mix up with other Savannah Sparrows, likely because they use different habitats: whereas Savannah Sparrows can be found in any kind of field, grassland or open areas with a few bushes, Ipswich is almost exclusively found in dunes and beaches, often feeding on the wreck.  

Phenotypically they also differ in so many ways – check out the pictures in the post and you will quickly notice how different they look from classic Savannah Sparrows. Ipswich are considerably larger, bulkier, with a bigger head and longer, more conical bill – they sometimes resemble a Lapland Bunting in structure and behaviour. They are also much paler and duller than classic Savannah, lacking the typical bright rufous fringes of the wing feathers and the contrasted black supercilium typical of Savannah. They also seem to differ subtly in their calls, being a bit higher-pitched than those of Savannah (see for instance here).

Ipswich Sparrow. October 2016, Massachusetts, USA. There is some variability on the level of brightness and contrast, perhaps related to sex and age

(Eastern) Savannah Sparrow, an autumn migrant of the savannah/oblitus/labradorius group. October 2017, Massachusetts, USA. A classic Savannah with contrasting plumage with bold face pattern, body streaking, and bright rufous fringes of wing coverts.

In October 2017, I was lucky to see a mixed group composed of 2 Savannah and 2 Ipswich Sparrows at Salisbury Beach, Massachusetts – both are seldom seen side-by-side so it was a great opportunity to compare their differences:

Ipswich Sparrow (front) with Savannah Sparrow (back). October 2017, Massachusetts, USA.

Ipswich Sparrow (back, left) with Savannah Sparrows. October 2017, Massachusetts, USA. Note the much bigger size and bulkier structure of Ipswich Sparrow.

Taxanomic Status

Although originally described as a separate species, Ipswich Sparrow was lowered to subespecies level in 1973 by AOU and its systematics hasn’t changed since then, although it surely will be revisited again in the future. Given the amount of differences and the low level of overlap with the mainland populations, Ipswich Sparrow would most likely have species status following the philosophy of most European taxonomic lists. However, to date all the taxonomic lists treat princeps as a subspecies of Savannah, likely due to the lack of specific studies proposing/considering the split.

Occurrence in the WP

The first Savannah Sparrow for the WP was actually an Ipswich Sparrow -  a bird seen in Devon (UK) on April 11th, 1982. This record has often been assigned to a ship-assisted bird and not fully accepted by some. Interestingly, most of the other records of Savannah Sparrow (presumed ssp savanna/oblitus/labradorius) were autumn birds, and this might well be related to the different migratory behaviour of both group taxa. Only the bird from Poland was found in spring/summer, but in this case date and location perhaps suggest that the bird crossed the Atlantic in the previous fall (just hypothesizing!). Given their migration over the Atlantic, mainly concentrated in October and April, Ipswich Sparrow might have a strong vagrancy potential, but likely weakened by its tiny population.

What do you think, should the status of Ipswich Sparrow be reviewed and perhaps added as a new species for the WP?

Ipswich Sparrow. October 2016, Massachusetts, USA.