About the beautiful bridled common murres.

1) Bridled common murres are not a different species or subspecies

Bridled common murres are the same species as the “regular” (non-bridled) common murres, the ring is is just a variation in looks.

2) They’re only found found along the Atlantic coast

The bridled variation is only found along the Atlantic coast, so Europe and East-coast America. Common murres also breed in the Pacific Ocean (from the gulf of Alaska until California), but the bridled variation is generally not found there. In 2008 researchers observed one bridled common murre in central California.

It’s not clear however if this variation naturally (but just very very rarely) occurs in common murres breeding in the Pacific area as well, or if the observed individuals were just lost Atlantic-ocean murres.

Read more about this:

• First record of the bridled morph of the common murre in the Pacific

3) They’re more common in the north

Bridled common murres are more common in northern regions than they are the south. Some colonies in Portugal are exclusively non-bridled, and by Bjørnøya (Svalbard) half the common murre population has glasses. At Hornøya around one third are bridled.

Read more about this:

• Distribution of the bridled form of the Common guillemot Uria aalge in the North Atlantic
• Quantitative Studies in the Geographical Variation of Birds – The Common Guillemot (Uria aalge)

4) They thrive better in colder temperatures

Bridled common murres seem to be better adapted for cold temperatures. Research showed that mortality amongst bridled common murres was highest after winters with higher temperatures of sea water. This could also explain why they’re more common in northern regions.

Read more about this:

• Climate fluctuations and differential survival of bridled and non-bridled Common Guillemots Uria aalge

5) The combination of parents influences the size of the chicks

Whether the parents are both bridled, both non-bridled, or mixed seems to play a role in the size of the chicks. Mixed parents, one bridled and one non-bridled, produced larger chicks compared to “pure” bridled and “pure” non-bridled pairs. Bridled common murres were generally the shortest.

Read more about this:

• Differential breeding investment in bridled and non-bridled common guillemots (Uria aalge): morph of the partner matters

More murre pictures can be found in my Common Murre / Uria aalge species collection, and prints can be found in my shop.