Eagles!

One of the cool things about Homer (and Alaska in general) is the number of Bald Eagles living here.  They are everywhere.  The first time I came to Homer in 2008 there was a woman dubbed "the eagle lady" who fed the eagles near the harbor.  As a result you would see them by the dozen sitting on pilings, along rock walls and on the tops of shops and homes.  She died later that year and there was legitimate concern as to what the eagles would do when deprived of one of their major food sources.  People with small dogs had to be particularly careful as eagles have been known to target them.  In the end they decided to continue feeding the Eagles through the winter and then slowly wean them off the unnatural food source.

Now, a few years removed from "the eagle lady", the eagles are still plentiful but are not as concentrated around the harbor.  Our country has perpetrated a few myths about eagles, portraying them as hunters descending on their prey with a mighty screech. While eagles do hunt for their food, consuming fish, birds or small mammals, they are also scavengers.  The best place in Homer to get photos of Bald Eagles is at the dump.  Eagles, along with the Glaucous winged gulls, are drawn to trash, dead animals and other easy meals.

As for the "mighty screech" that you often hear on TV, whoever first put eagles on film decided that the eagle's actual call was too wimpy to be associated with America's mascot.  Instead they dubbed in the voice of the Red Tailed Hawk which provides that classic screech. Here is a video of a Red Tailed Hawk's call, and here is a Bald Eagle's call.  The eagle's call is quite beautiful but it is not what you would expect from such a large, powerful bird.

Interestingly, the juvenile eagles often appear larger than the adults.  This is due to the juvenile's feathers which are longer and heavier than those on an adult eagle.  The juvenile feathers serve as "training wheels" while young eagles are learning to fly.  The adult's smaller feathers allow them to fly more gracefully and with greater maneuverability than the younger eagles.

Juvenile Eagle between two adults

Despite the cynical attitude I've treated eagles with in this post, I still stop an admire them when they soar past.  They add to the majesty of this place and it is a privilege to be able to see them with such frequency.

Layers of complexity

This photo was taken near Kasitsna bay, where we occasionally run programs.  At first glance the subject of the photo appears to be a striped hermit crab.  The picture itself isn't bad, the colors turned out well and the lighting is nice, but if you look again at the hermit crab you might start to notice some things.

Click for full size

  First of all, the shell that the hermit crab is using is red.  This is because the hermit crab is living inside a wandering sponge.  There are some species of sea sponge that will attach themselves to snail shells and slowly consume the shell until nothing is left but the sponge. Once the snail is dead it is not uncommon for a hermit crab to move in and allow the sponge to continue its wanderings.  

Not many things eat sponges; they are full of sharp spicules that can wreak havoc on a creature's digestive tract.  In an earlier post I covered mollusks and talked a little bit about Nudibranchs, which often eat organisms that nothing else will.  The yellow blob you see sitting on top of the hermit crab is actually a False Lemon Peel Nudibranch that specializes in eating sponges.  

To recap, a wandering sponge began growing on a snail shell which was then inhabited by a hermit crab.  The sponge attracted a nudibranch which is now eating the hermit crab's home.  If you've been following this blog you should be able to name two of the three phylums represented in this photo.  Athropods are represented by the crab, Mollusca by the Nudibranch and Porifera by the sponge.

Even after three seasons of doing this, I'm still consistently amazed by the things that show up on our beaches.

Fab four Phyla part four: Arthropoda

Arhtropoda is the largest and most diverse phlyum on Earth.  The pre-fix Athro refers to joints (as in arthritis) and pod means foot, so the name arthropod refers to animals with jointed feet or legs. The phylum arthropoda encompasses organisms such as insects, spiders and crustaceans.  Besides having jointed legs, athropods also have segmented bodies and a tough chitinous exoskeleton that they occasionally molt.  On our beaches we see mostly crustaceans; i.e. crab, shrimp and barnacles.

Black Clawed Cancer Crab
Its large claws are used to crush barnacles

Most people don't realize that barnacles are so closely related to crabs and shrimp.  Barnacles begin their life as a plankton and as they grow larger they change through various stages until they become a cyprid.  The cyprid's task is to find a good spot to settle on the sea floor and become a barnacle.  They land head first and begin to create a hard, 6 plated calcium shell around themselves.  To feed, they kick out their feet, which are shaped like tiny fans, and collect their food from the water.  We just recently had a barnacle fall out in our area and now everything is coated in the brittle white shells of young barnacles.  You feel bad crushing so many animals underfoot but our beaches are just so packed with life that it is impossible to do otherwise while tidepooling.

Empty molt of a helmet crab

There are several species of crabs on our beaches, though none of them are popular commercially.  Decorator crabs are my personal favorite.  Decorator crabs do not have large claws to protect themselves with, instead they rely on camouflage.  Using their narrow claws, they hang algae and other things from the tiny hooks on the carapace until the blend seamlessly into their environment.  It is nearly impossible to see a decorator crab unless it is moving.  Taking one out of water, they become spider-like, with long narrow legs and a proportionately small body.

A friend holding a decorator crab

Hermit crabs are another popular arthropod found on our beaches.  We have a few different varieties ranging in color from a drab brown to a brilliant orange.  Hermit crabs appropriate the empty shells of other organisms (usually snails) to give themselves additional protection.  Their body curls to fit into the shells and they have legs specifically adapted to hanging onto the shell.  One of their claws is generally over sized and acts as a shield to cover the entrance to their home.  We keep several large hermit crabs in our touch tanks at the field station and you can often watch them squabbling over new shells.

Helmet crabs mating

  At one point there were several species of crabs in Kachemak bay that were commercially important to Homer.  Tanner crabs, Dungeness crabs and King crabs could all be caught in the bay during the late 70's.  No one is exactly sure why the fisheries collapsed; whether it was due to mismanagement, a fuel spill, or just part of a natural cycle, these species no longer exist in Kachemak bay in harvestable numbers.  The Tanner crab and Dungeness crab populations are slowly recovering and hopefully they will continue to do so.

An Orange Hermit crab from our touch tanks