Re: Reporting the Nazca/Masked Booby


Peter Pyle
 

This may help -
https://www.birdpop.org/docs/pubs/Pyle_2020_Molt_Age_and_ID_of_MABO_and_NABO.pdf

I remain confident that this was a Nazca based on the concave and lumpy bill shape with bulbus tip (giving overall skinny look to the bill) and dusky/blackish bill base, perhaps tinged dull pinkish in some images, and golden/yellowish tip in brighter images, such as Joe Morlan's here:
https://macaulaylibrary.org/asset/481501681
(https://ebird.org/checklist/S118167268)

Masked has a more conical shape to the bill and green tones (see Figure 5 in above paper).

The small extent of exposed white at the base of the central rectrices is found in both species, including about 30% of Nazcas (with 12% of Nazcas showing no white). The lack of white in the hind collar is also an average or better character for birds at this young age. It looks like it has not begun flight-feather molt yet ,or perhaps p1 dropped on the right wing and middle tertial on the left wing, which would put it at 7-9 months old.

Nazca has become the much more prevalent species of the two up here. It is more of a coastal species than Masked (Peruvian current), less tropical. Given persistent cold (La Nina) waters over the past couple of years I'm not surprised that this trend continues, although with seabirds it seems anything is possible.

Good birding, Peter

At 08:51 AM 9/6/2022, Dominik Mosur wrote:
I would like to add one more thing , for those who observed and photographed this bird — woukd you please crop the images so that it can be more easily ascertained.

Thank you everyone!

Stay cool,
DM


On Sep 6, 2022, at 08:44, dominikmosur@... wrote:

thank you!

Realized that a little while after posting.




On Sep 6, 2022, at 08:42, Steven Tucker <talkingtrees80@...> wrote:


Hi Dom and all, FYI both Nazca and Masked have been removed from the CBRC review list in recent years. In fact, the only Sulid on there currently is Northern Gannet - not a situation I would have expected a decade ago.

Steve Tucker
Salinas, CA

On Tuesday, September 6, 2022 at 08:34:15 AM PDT, Dominik Mosur <dominikmosur@...> wrote:


A quick message regarding the Booby observed yesterday from Battery Godfrey. I’ve heard differing opinions on the identity of this bird with some favoring it being a Nazca while others opining that because the bird is a subadult it may be difficult if not impossible to identify to species.

For anyone who observed this bird I urge you to send a report to the CBRC (California Bird Record Committee) and include any photos.

Here’s a link to their submission page:

<https://californiabirds.org/report_sighting.html>https://californiabirds.org/report_sighting.html

Great find, Hugh.


Please contact me if you have any questions.

Dominik Mosur
San Francisco

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