Thursday, September 2, 2010

Of Higbee's, Gulls and Pseudo Monarchs!

Higbee's Beach has been well up to its usual standards this past few days and, with it being so early in the season, there is currently few birders treading the paths - though numbers are slowly increasing daily. With most of the keen eyes and ears up on the dike, I felt the fields were getting short shrift so I've been working them whenever I get a chance. So far this month, American Redstarts, Black-and-white Warblers, Red-eyed Vireos and Northern Waterthrushes have been by far the commonest species present, but on September 1st, Veeries gave them a run for their money, with a good number calling from the thicker vegetation blocks. This morning several Black-throated Blue Warblers, a Blue-winged Warbler and several Chestnut-sided Warblers were noted but the highlight was the logging of at least three Philadelphia Vireos.

This Philadelphia Vireo proved difficult to photograph as it hunted insects avidly amongst the Black Cherries, but it gave more than adequate views when it came down to chest level in low vegetation and ended up flying straight at me before swerving off and back into the treetops - must be hurricane fever! [Photo by Mike Crewe]

A welcome change in habitat management will be apparent to those visiting Higbee's Beach WMA this fall. Gone is much of the regenerating scrub, to be replaced by annual plants, sown to attract seed-eating migrant birds. This juvenile Dickcissel was enjoying the sorghum seed ripening in field 3 [Photo by Mike Crewe]

With Monarch migration well and truly under way now and the Monarch tagging team getting ready for another busy season, it's as well to get an eye in on a trap for the unwary. This is a male Monarch....

....but this isn't (with apologies for a rather scruffy individual!). This is a Viceroy, a species in the Nymphalidae - the family which contains the fritillaries, admirals and ladies among others. The most obvious difference here is the narrow black line which runs across the hindwing - a feature which is quite easy to see and can even be seen in flight if you know to look for it. Other more subtle differences include the single rather than double row of white spots around the margin of the wings and the lack of white spots on the head.

Underneath, too, the similarity is uncanny - here a Monarch....

....and here a Viceroy. Note that the Viceroy has mastered a few white spots on the body and has the shades of orange right too! Another easy way to tell the two species apart is by the way they fly; Monarchs drift effortlessly with lazy, bouyant flaps interspersed with long glides on wings that are held in a 'V', like the dihedral of a Turkey Vulture. Viceroys on the other hand, use a rapid series of busy flaps, followed by a glide on out-stretched, flat wings. If you want to get your eye in on this flying technique, watch the widespread Common Buckeyes which are closely related to Viceroys and which fly similarly. [Photos by Mike Crewe]

If you want to see a Viceroy at Cape May, the best place right now is at the Beanery - and remember that one of the great benefits of CMBO membership is free access to this excellent farmland location. The Viceroy is a well-known Monarch mimic - Monarchs of course being poisonous due to the chemicals that they assimilate from their foodplant (Milkweed species). It was long thought that Viceroys were so coloured so as to benefit from being mistaken for Monarchs by would-be predators and left alone as they would be presumed to be poisonous also. This is called Batesian mimicry, where a non-harmful species benefits from looking like a potentially harmful one. However, it now seems, after more recent research, that Viceroys themselves are poisonous too. This form of mimicry, where two or more potentially harmful species look alike, is known as Mullerian mimicry and probably works as the species all benefit from potential predators
learning that they are harmful after taking just a small sample size - after which they are all left alone!

One of those messy gulls again! I was pleased to find this Lesser Black-backed Gull at the South Beach this evening, then discovered that Tom Johnson had seen four earlier on! Oh well, it's another one of those mid-molt photos to get gull fanatics drooling; this is a third-calendar year bird (or what ever other far more complicated term you may prefer to use!) molting into its third-winter plumage, which nicely shows a strong contrast between the old, brown wing feathers and the new, grey ones. Notice how the median coverts have been molted in a line along the center of the wing first, and notice how the primary coverts are each molted in tandem with their respective primary. [Photo by Mike Crewe]

And finally, with a hurricane passing close by and potentially giving us some weather to reckon with, it's nice to see that even the birds are hunkering down and taking precautionary measures! [Photo by Mike Crewe]

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