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One of the things that is expected from me with my internship through Monterey Bay Aquarium and their Sea Otter Research and Conservation department is a project. The stress of coming up with something and presenting it was stressful. I jotted down thoughts and ideas that could potentially turn into a project and finally decided that I really wanted to incorporate gulls (Western gulls – Larus occidentalis). I would study the interaction between southern sea otters and western gulls.

Sea otters need to eat a 1/4 of their body weight a day, so you can imagine they spend quite a bit of time foraging. What’s on the menu? Sea otters will eat quite the variety of animals, consisting of crabs, urchins, clams, mussels, snails, and other invertebrates. Western gulls, being so opportunistic, like free handouts and following sea otters to gobble up what they can is very common. Sea otter dives typically don’t last more than a minute or two and while that otter is down and you are looking through a scope trying to find out where they are going to pop up next, the sight of a gull with a sea otter can be your best friend because they are right there waiting at the surface.

My first challenge in this project is simply identifying Western gulls and what cycle of plumage they are in and that is what this blog is going to hopefully clarify (for you and me). It takes four years for gulls to become an adult. This poses the question- are juveniles, adults, or somewhere in between successfully mooching off sea otters? Are they competing for the same food sources? Some gulls can be quite aggressive in their efforts and sea otters have been known to actually drown and consume birds.

Western gulls have some general characteristics including their large size, dark slate gray back, pink legs, and white head and underparts. The ones located around Monterey are there year-round, so being able to see the different plumages is relatively easy. Technically you have juvenile, first winter, first summer, second winter, second summer, third winter, and the third summer plumages, which makes identifying them seem a bit daunting. For the purpose of my study, they are labeled as a #1, 2, 3, or 4.

A #1 is a year old bird including the juvenal and first winter plumage. A #2 is a second year bird including its first summer and second winter plumage. A #3 is a third year bird including its second summer and third winter plumage. A #4 is the third summer and includes adult plumage. Not too hard right? Then again, they can hybridize and individuals can have variability in plumage! ::whew::

Lesson Overview:

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#1

– Black bill
– Dark eyes
– Overall dark plumage
– Dark legs with pink overlay

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#2

– Bill lightens at the base
– Heavy mix of grey and brown feathers
– Head is starting to lighten

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#3

– Looks very similar to an adult
– Head still mottled and not virtually all white
– Tip of bill still black

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#4

– Bright yellow bill with red spot
– Yellow iris
– Dark grey back
– Apical spots on black primaries
– White tail

. End of lesson . now POP QUIZ!

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