Warbler Wars – the facts, the stats, the pictures

Scope of Work
This blog post investigates the nagging notion that warblers of the Old World are drab and boring interesting on multiple levels especially to the extreme bird enthusiast while North American wood-warblers are nothing but beautiful and magical. I have tried to go beyond the emotional perception and actually analyse the colours on the bird, species by species and colour tone by colour tone, to finally put the affair to rest.

Method
To accomplish this, I have taken the easy road, by which I mean I have taken two field guides and flipped through them instead of using check lists. Therefore, the species involved are those wood-warblers depicted in the large edition of the Sibley guide and all the warblers that are in Jonsson’s guide to the birds of Europe (Jonsson’s guide because the German edition also has the English names of the birds, compared to my edition of the much newer guide by Svensson et al.). Very curiously, the number of species included in this study were 55 for both regions.

I then looked at the different colours of the birds, defining colours very broadly by also including black, white (and thus also grey), and brown. The list of colours I discriminated between is here:

brown, black [that’s not a gap, it’s “black”], grey, white, red, orange, yellow, green, blue.

Determining the colour was not always as straight forward as it may seem, e.g. I have found it difficult in some cases to distinguish grey from blue and red/yellow from orange. But overall, I feel it worked out okay.

The Northern Parula turned out to be the most colourful of the wood-warblers, and I assigned this species the colours black, white, grey, green, yellow, and red.

Results
[Europeans may want to sit down while Americans may want to get themselves some enjoyable beverage]

1.     Number of Colours per Species

North American wood-warblers sport, on average, a staggering 3.98 colours.
European warblers sport, on average, a less impressive 2.6 colours.
Furthermore, there are significantly more warblers with 4 or more colours in North America than in Europe, while there is not a single North American wood-warbler that is characterized by only one colour, which happens occasionally in Europe.
Here is the graph to visualize what the East side of the Atlantic won’t like to see visualized:

The Blackcap, a  true stunner amongst the European Sylvia warblers. Here, a male (black cap) is feeding berries to his offspring, a “female-coloured” bird to its right.  You just gotta love the cunning combination of grey, black, and brown. And it’s even got sexual dimorphism – whoa!

2.     Relative Abundance of the respective Colours
Of course the number of different colours doesn’t mean all that much when I have included such “colours” into this inquiry as brown, black ,grey and white. Therefore, aside from the number of different colours per species, the relative abundance of each colour in all the species needed to be analysed.

Look below for a visualization of the results:

This comparison is really where I encountered the biggest problem of my inquiry: there was no taking into account the area covered by a certain colour on the bird I was investigating. You see,  bird 1 could essentially be mostly coloured in bright yellow with only a slight touch of brown on the rump and bird 2 could be entirely brown with just a tiny spot of yellow on the lores, and both would be of identical impact on the graph seen above. This will explain why colours such as white and black are so dominant, yet neither North American nor European birders would perceive their (wood-)warblers as being coloured this way.
To account for this, I have repeated this test and only considered the most dominant colour on a bird, the one that would psychologically define our perception. A Black-throated Blue Warbler therefore only “gave” its blue part while any Acrocephalus warbler “lost” its white and bits of black and just entered its brown part into the game.

A Marsh Warbler, a typical Acrocephalus that is finely patterned in different shades of brown with a bit of white, but “corrected” must stand and fall as an essentially brown bird – and brown only bird.

The shocking result of the “corrected” colour abundance is given in the graphs below.

Oh dear, does the Old World look bad now. Mostly brown (Reed Warblers, Locustella warblers, etc.), green (Phylloscopus warblers), and grey (Sylvia warblers), with a bit of red (some choice male Mediterranean Sylvia warblers that we scarcely get to see anyway).
And North American wood-warblers? Well, yeah, they are just … colourful, okay? But I bet you never realized just how dominant yellow is.

This Northern Waterthrush may be a wood-warbler, but it is brown. See? Brown, brown, nothing but brown. Mwahahahahaaaaaaa …

Summary of the Results
The nagging notion that warblers of the Old World are drab and boring interesting on multiple levels especially to the extreme bird enthusiast while North American wood-warblers are nothing but beautiful and magical is sadly, tragically, unjustifiably, yet essentially and objectionably objectively  TRUE.

Boy, do I need to re-visit North America in spring now…

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This week, 8 May – 14 May 2011, is Wood-Warbler Week on 10,000 Birds!  Though wood-warblers, the mostly brightly colored birds of the family Parulidae, are only found in the New World we felt that birders the world over would be pleased to see a plethora of posts about these striking and sought after species.  We are devoting a whole week to wood-warblers but are only just barely scratching the surface of possible topics involving this amazing family of birds.

Right now great flocks of wood-warblers are making their way north from the southern United States, Mexico, the Caribbean, Central and South America to breed across the United States and Canada.  Many other non-migratory wood-warbler species are living their lives across the neotropics, doing their best to survive and pass on their genes. Wood-Warbler Week is a celebration of all wood-warblers and we hope you join us in celebrating these absolutely wonderful birds.  Read about them here but also getout and experience them.  You won’t regret it!

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