Tag Archives: Biology

An Ivory Gull in Duluth, So What?

What does it mean when one of the least researched and understood marine birds in the Arctic turns up in Duluth, Minnesota 1,500 miles outside of its range? Locally, it ensures a birding rush of in-state and out-of-stater birders eager to see the rare bird, but what does it say about the global status of this unique bird? How can we use its presence to  educate ourselves of human impact on the high Arctic? Is the Ivory Gull (Pagophila eburnea) an indicator species of a greater issue in the Arctic? The suspicion that their unprecedented, 80% population decline over the last 20 years may be linked to mercury suggests they are.

Ivory Gull, Duluth
The Ivory Gull at Canal Park in Duluth sits on the piers a few hundred feet from the human observers on shore.

Population Free-fall of the Ivory Gull

Ivory Gulls are colonial birds, meaning that large numbers gather into groups to breed. By monitoring the nesting colonies of colonial birds, population trends may be established by researchers. However, surveys for Ivory Gulls  were only conducted in 1985 (Thomas and MacDonald, 1987) making it impossible to understand population trends. Compounding the lack of population data, Ivory Gulls are considered to be one one of the least understood marine birds. This is partly due to wintering along the ice pack between Greenland and Labrador ensuring they are not a bird which is in-sight of many people. However, indigenous knowledge has suggested declining populations since the 1980s (Mallory et al. 2003). In light of this, researchers  flew surveys of known nesting islands as well as newly found Islands in 2002 and 2003 and found something shocking. The number of nesting Ivory Gulls had declined by 80% since the 1980s (Gilcrest et al. 2005).

Ivory Gull, Identification
The Ivory Gull is a distinct bird with a blue bill, black feet, and stunning black tips on the wings.

Gilcrest et al. (2005) started to hypothesize at alternative reasons for the lack of gulls. They explored the possibility that the Ivory Gulls had simply shifted their nesting locations. However, a significant move is not inline with the known biology of the bird which generally move less than 1-2 kilometers.  Food sources of fish and carcasses have remained relatively stable in their study area giving them little reason to move. They noted that Ivory Gulls were not seen flying along the survey paths. It seems that the Ivory Gull was truly dying off.

Ivory Gull, Duluth, Minnesota
In Duluth, the Ivory Gull was gracious enough to land close to my camera, offering exceptional looks at the details of this beautiful bird.

 

The Driver of Change

Since the startling revelation of population decline, researchers have been trying to understand why Ivory Gulls are disappearing. It is probable that ice-pack changes and altered forage have contributed to the population decline (Gilchrest et al. 2005), but researchers think a stronger factor is in play . In his interview with the BBC World Service (full interview below) Dr. Alex Bond  hypothesizes that mercury is a leading stressor on Ivory Gulls based on findings that levels of mercury have risen 45 -50 times the levels found 130 years ago. There is strong evidence showing mercury levels in the eggs of Ivory Gulls is significantly higher than any other known marine bird. Braun et al. 2006 found that mercury in the eggs of Ivory Gulls were 2.5 times greater than even the next highest species, and were almost 3 times greater the amount which impairs reproductive success. Where is that much mercury coming from? And how exactly might it effect Ivory Gulls?

Ivory Gull, Underwings
The Ivory Gull in Duluth shows off its beautiful, white underwings.

To understand where the mercury is coming from, its important to know the basics of the mercury cycle. Mercury falls into the oceans from atmosphere pollution originating from coal-fired power plants, or is directly input from Alkali metal processing . There are also natural sources of mercury like volcanic eruptions and “volitilization of the ocean” (USGS 2000).  Once deposited in a waterbody, mercury becomes available to marine animals when it is transformed to methylmercury. Once in the that state, it moves up through the food chain into plankton, and then to fish, and finally to top level predators like birds and marine mammals.  Levels of mercury grows in organisms through bioaccumulation and biomagnifcation. To clarify that jargon, bioaccumulation means that the older you are, the more mercury you have since it is difficult to get it out your system once ingested. Biomagnification means that if you feed higher on the food chain you gain mercury more quickly. Marine mammals like seals have very, very high levels of mercury due to the effect of both bioaccumulation and biomagnifacation. With that information in mind it is easier to understand why Ivory Gulls accumulate mercury; they scavenge on carcasses of marine mammals and feed on fish which have high levels of mercury. They also have a high metabolic rate and consume more fish (Braun et al. 2006).

To date, the effect of mercury on Ivory Gulls has not been studied, but we can gather clues from looking at other species.  Common Loons (Gavia immer) also accumulate high levels of mercury due to eating fish (biomagnification) and having long lives (bioaccumulation). Evers et al. 2008 found a 41% decrease in fledged loon young in parents with >3 micrograms of mercury per gram of tissue compared to those with <1 microgram. They predict total reproductive failure of Common Loons if levels exceed 16.5 micrograms. Based on hundreds of hours of observation, they report that loons with elevated levels of mercury are lethargic and spend significantly less time foraging for food and less time taking care of their young. Each lead to fewer chicks growing to adulthood.  It is important to note in their study that mercury levels of a species change throughout their range due to climate, forage, and many other factors. Transferring the lessons of Common loons to Ivory Gulls, variation in  mercury levels changes are observed in Canada as well; in general levels of mercury increase from east to west in Canada. Although the effect of mercury on Ivory Gulls has not been directly studied and may effect gulls differently than loons, a good hypothesis for their decline is poor parenting and lethargy due to extraordinarily high levels of mercury. Only future research will help tease out the true effect of mercury on their decline.

Ivory Gull, Flying, Duluth
The Ivory gull in Duluth takes to the wing showing off its beautiful plumage and black feet.

When an Ivory Gull shows up in Duluth, Minnesota it is a chance to reflect. Reflect on the beauty of an animal. Reflect on the joy of seeing such a rarity. However, do not miss the opportunity to acknowledge that its prescense is out of the norm of the species and that an unseen driver which we do not fully understand is at play. Reflect on the fact that the impact of humans in a nearly un-inhabited region is undeniable. Human consumption of fossil fuels is depositing mercury into the Arctic at rates which may be directly effecting a species. The Ivory Gull is a red flag, an indicator that things are not right in the Arctic and that we should pay heed to what else may be going wrong that we just have not taken the time to study yet.

Sources:

http://www.bbc.com/news/science-environment-31921127

Braune, B. M., Mallory, M. L., & Gilchrist, H. G. (2006). Elevated mercury levels in a declining population of ivory gulls in the Canadian Arctic. Marine Pollution Bulletin, 52(8), 978-982.

Evers, D. C., Savoy, L. J., DeSorbo, C. R., Yates, D. E., Hanson, W., Taylor, K. M., … & Munney, K. (2008). Adverse effects from environmental mercury loads on breeding common loons. Ecotoxicology, 17(2), 69-81.

Gilchrist, H. G., & Mallory, M. L. (2005). Declines in abundance and distribution of the ivory gull (Pagophila eburnea) in Arctic Canada. Biological Conservation, 121(2), 303-309.

Mallory, M. L., Gilchrist, H. G., Fontaine, A. J., & Akearok, J. A. (2003). Local ecological knowledge of ivory gull declines in Arctic Canada. Arctic, 293-298.

Thomas, V.G., MacDonald, S.D., 1987. The breeding distribution and
current population status of the ivory gull in Canada. Arctic 40,
211–218.

USGS. 2000. http://www.usgs.gov/themes/factsheet/146-00/

https://soundcloud.com/bbc-world-service/ivory-gull-decline

A Short Documentation of Life on A Milkweed Plant

During one of my forays with the Herbaceous Jellyfish (ie: thistles) on our land I observed one of the most bizarre bugs that I have seen. It had the head of a mantis and a long neck/thorax area that connected to claw like pinchers. From that point the body of the insect became wasp like with wings and a bulbous abdomen. It was orangish-red in color and had stripes. WHAT IS IT?!?! A google search at home by Kass for “bug that looks like wasp and mantis” quickly revealed that I had discovered a mantid fly. Unfortunately, at that time I didn’t have my camera with. So, a couple of days ago I made it a point to bring my camera up to the land and try to document these bugs. I soon found out that they were quite common throughout the thirty acres of pasture, and were obligatorily associated with the milkweed clusters throughout the pasture. Fortunately they were almost fearless and allowed me to get nice and close. So, before I go into my thoughts on these bugs I thought I would throw a few pictures out here first to bring your attention to the uniqueness that I’m talking about.

P7230170
Mantid Fly on a Milkweed Plant
P7230062
Look at those Mantid Eyes!

 

You’ll notice that it has pinchers just  like a mantis. In an attempt to discover what this bug ate, I skewered a small deer fly on a 12 inch blade of grass and dangled it in front of the mantidfly. It struck out at the dangling fly and continued to back up and run down the stem of the milkweed. He wanted nothing to do with this large insect in front of him! In fact, my prodding caused him to use his wings and flee in flight. I’m assuming based on these results that the mantidfly focus on smaller prey such as fruit flies and aphids. In almost all cases these bugs were tucked underneath leaves or at least close to cover. I think they are afraid of being eaten. After examing many milkweeds I found two cases were a dead mantid fly was tucked against the milkweed stem. It seems they are also very territorial! I can only assume/guess that the carcasses were there because of homicide from another mantidfly. Here another pictures that displays the bizzare figure of this creature.

P7230182

However, during my close examination of milkweeds I became fascinated with the number of insects that I observed using the milkweed. I took pictures where the creepy crawlies allowed me to demonstrate just how important milkweed is. One of the things I saw were these aphids clinging to a leaf. They numbered in the hundreds if not thousands.

P7230125
Aphids clustered up for “farming” on a milkweed.

These aphids would be an easy snack for the predatory lady bug. It was hunkered just above them. I’m sure that he was sitting there after just having his big feast of tender, juicy bugs. I almost felt sorry the aphids, however, they were not without armor and defense!

P7230118
This lady bug is looking for an easy aphid snack. I bet it’s an easy dinner!

Ants, which covered the milkweed were defending the aphids and caring for them. I saw them interact with the lady bug several times and each time the lady bug recoiled from the ants. I don’t think the ants are able to hurt the lady bug, however, they can still help defend the aphids. So why, you might ask, would the ants defend the aphids? They would be a great, easy meal for the ants as well! However, ants and aphids are symbiotic and actually help each other! The Ants take care of the aphids in turn for the sugary liquid that is expelled from the aphid’s butt. You can see the liquid being expelled for collecting below! Also pictured are the number of aphids that covered the milkweed as well as the number of ants.

P7230129
This ant is reaping the benefit of taking care of its defenseless aphids (sheperd and sheep). He’s sucking the energy rich excretion from the aphid.
P7230126
There are a lot of aphids and ants on one milkweed flower!

 

I also saw many examples of spiders that inhabit the leaves and flowers a milkweed, however, only a couple of them hung around for pictures. Here is another example of life and death on the milkweek plant. This crab-spider has caught and is chowing down on an ant. I’m sure he has no problem catching as many as he needs.

P7230141
It’s dinner time for this unknown species of grab spider. Ants for breakfast, supper and lunch!

P7230097

I also saw several examples of this black-spotted red bug. If you happen to know the name of this one let me know! They are pretty unique.

P7230113
I’m unsure of the species of these red bugs, but they were fairly common throughout the milkweed patches.

On of the great things to see was the amount of honey-bee activity happening around all of the milkweed patches. We have bee hives on our land and our pasture is a reliable source for the bees to get pollen, and they do us a favor by pollinating our flowers. The bees can be a bit aggressive however. I was stung on the day I took these pictures while standing 60 feet from the hives. I’m not sure what inspired the bee to jab himself into my back, but I was glad none of his friends follow suit.

P7230082
Our land has hives on it and the milkweed were a predominant source for the bees at this time of year. There many flitting around each flower. One thing that was interesting was there were also many dead ones on the flower. I’m not sure if that’s a bad sign from inside the hive, or a natural process.

Another one of the insects to inhabit the milkweed patch were the dragonflies. There were several varieties ranging in colors of black to yellow and orange. And, in size from 1.5 inches to 3 inches. There were some really huge dragonflies. I have seen the large dragonflies take bumblebees before and I’m convinced that a large dragonfly will also cannibalize his smaller cousins and fellow species. While walking through pasture I felt one smack into the back of my head, picking a deer fly away from there in the process. The one pictured below is actually a different deer-fly kill than that one! Based on this evidence of two kills I think the take of deer flies by dragon flies must be pretty large! I hope it’s painful for the deerfly – they earned it. Note, this one wasn’t on a milkweed plant, but he was juxtaposed directly to a patch.

P7230095
Redemption! I was thrilled to see this dragonfly happily munching on this deerfly.

One last random insect on the plants was this great/blue bottlefly.

P7230136

Of course the one thing I haven’t hit on here at all was the number of butterflies that were using the milkweeds. There were many, but my lens didn’t have enough zoom to do many of them justice as they were skiddish and flighty.

The pictures here show a one hour glimpse of life on milkweeds. It’s amazing when you start to focus on the small things around you the details you will pick up, and there are many that you miss! Be sure to stay observant to your surroundings, and that means more than the physical. There are tiny details in the commons places of our world and personal relationships to entertain, teach and humble.