//
you're reading...

Behavior

By the Light of the Night: Abiotic factors limit Arctic seabird foraging

"Thick-billed Murres in Alaska refuge" by Sowls, Art - U.S. Fish and Wildlife Service

“Thick-billed Murres in Alaska refuge” by Sowls, Art – U.S. Fish and Wildlife Service

Elliott, K., & Gaston, A. (2015). Diel vertical migration of prey and light availability constrain foraging in an Arctic seabird. Marine Biology, 162(9), 1739–1748. doi:10.1007/s00227-015-2701-1

Background:

With climate change expected to increase the severity of summer storms and expand species’ home ranges towards the planet’s poles via rising temperatures, understanding the impact of, and interaction between, physical (abiotic) and biological (biotic) factors on an organism’s fitness is of great importance. Historically, when assessing foraging behaviors in seabirds, scientists have relied on biotic factors—such as prey availability and competition for resources between predators. In contrast, this recent study by Elliott & Gaston sought to highlight the influence of abiotic factors by observing a colony of Low Artic thick-billed murres (Uria lomvia) on Coats Island, Nunavut. Weather conditions, tidal currents, and light availability were of primary interest to see how these birds altered their diving behavior when searching for food.

Thick-billed murres are visual predators that will readily eat amphipods (small crustaceans), sandlance, or cod. Many of the preferred prey items perform migrations within the water column over the course of the day, requiring a degree of malleability in the foraging behavior of the birds. Additionally, wave action, tides, and levels of light intensity all affect visibility and access to prey beneath the water’s surface. Intense storms can generate waves that prohibit murres from accessing prey, tidal currents can alter the availability of preferred prey, and light availability will limit the depths to which murres can successfully locate and capture prey. Therefore, Elliott & Gaston hypothesized that high wind speed (and greater wave action) would reduce dive frequency, tide height would increase dive depth, and limited light availability would reduce dive depth and duration.

Methods:

The monitoring of the murre colony spanned 1998-2011; every year from July 15th -August 15th a minimum of three continuous 24-hour watches occurred during which prey items were remotely counted by researchers visually assessing incoming murres returning from dives to one of approximately 30 colonies. The most identifiable prey items were fish or larger benthic organisms. Ingestion of small prey like amphipods was confirmed by stomach content analysis in a separate study.

Fig. 1: Coats Island is located in the northern portion of Hudson Bay, just south of the Arctic Circle.

Fig. 1: Coats Island is located in the northern portion of Hudson Bay, just south of the Arctic Circle.

From 2004 to 2009, 210 adult, breeding birds with chicks 3-15 days old (that is, chicks requiring constant feeding) were tagged with time-depth recorders to note frequency, depth, and duration of dives while out foraging.

Weather conditions (temperature, rainfall, barometric pressure, wind speed, and wind direction) were recorded both at the study site and at the nearby community of Coral Harbour. Additionally, periods of twilight were recorded for each day of observation. The geographic location of Coats Island (Fig. 1) places it just south of the Artic circle; during summer, true darkness at night is exceedingly brief.

Results:

Of the abiotic factors (tidal currents, wave action, and light availability) examined, light availability was the only component that significantly impacted dive depth of the thick-billed murre. Dives tended to be longer and deeper when light intensity was higher, although the overall number of dives made during peak light was lower. As seen in Fig. 2, dive depth was closely linked to time of day; the only significant difference noticed was between males and females. Previous work had already established that males foraged during the night while females foraged during day. Aside from this divvying of foraging times, female birds continued to dive deeper than males later in the day. This suggests that the preferred prey items have been separated between males and females, along with the foraging times. Females may have specialized on the deep-water prey (fish) that is available at their foraging time, while males may have specialized on amphipods that are actively migrating up and down in the water column.

Average dive depths of 56 male (dark circles) and 48 female (empty circles) thick-billed murres between 2004 and 2009.

Fig. 2: Average dive depths of 56 male (dark circles) and 48 female (empty circles) thick-billed murres between 2004 and 2009.

Indeed, the natural migratory patterns of prey were also reflected in the catches of diving murres. Delivery of high-energy foods like sandlance peaked in the early hours of the day while benthic organisms were delivered primarily in the middle of the day (Fig. 3). These catches were also affected as the season progressed, as schooling fish were harder to catch during stormy weather, or as local stocks were depleted.

Delivery of high/low energy prey items, separated by time of day as observed from 1998-2011. Hours of decreased light were excluded as prey were rarely delivered to nests during these hours.

Fig. 3: Delivery of high/low energy prey items, separated by time of day as observed from 1998-2011. Hours of decreased light were excluded as prey were rarely delivered to nests during these hours.

Big Picture:

While these results may seem trivial, this study highlights the importance of considering abiotic factors when assessing population fitness. Coats Island is a remote study site, and few monitoring programs are in place to provide insight into the health of the Arctic ecosystem or this part of Hudson Bay. When reflecting on the predicted climactic shifts expected in the coming century, fundamental knowledge about the malleability, specialization, and robustness of foraging behaviors becomes crucial. Data like this provides hints as to the success of a species; if the thick-billed murre does press further north and appropriate prey are there, the light of the summer night should be more than enough for them to see by.

Discussion

No comments yet.

Post a Comment

Instagram

  • by oceanbites 3 weeks ago
    Not all outdoor science is fieldwork. Some of the best days in the lab can be setting up experiments, especially when you get to do it outdoors. It’s an exciting mix of problem solving, precision, preparation, and teamwork. Here is
  • by oceanbites 1 month ago
    Being on a research cruise is a unique experience with the open water, 12-hour working shifts, and close quarters, but there are some familiar practices too. Here Diana is filtering seawater to gather chlorophyll for analysis, the same process on
  • by oceanbites 3 months ago
    This week for  #WriterWednesday  on  #oceanbites  we are featuring Hannah Collins  @hannahh_irene  Hannah works with marine suspension feeding bivalves and microplastics, investigating whether ingesting microplastics causes changes to the gut microbial community or gut tissues. She hopes to keep working
  • by oceanbites 3 months ago
    Leveling up - did you know that crabs have a larval phase? These are both porcelain crabs, but the one on the right is the earlier stage. It’s massive spine makes it both difficult to eat and quite conspicuous in
  • by oceanbites 3 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring Cierra Braga. Cierra works ultraviolet c (UVC) to discover how this light can be used to combat biofouling, or the growth of living things, on the hulls of ships. Here, you
  • by oceanbites 3 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Elena Gadoutsis  @haysailor  These photos feature her “favorite marine research so far: From surveying tropical coral reefs, photographing dolphins and whales, and growing my own algae to expose it to different
  • by oceanbites 4 months ago
    This week for  #WriterWednesday  on Oceanbites we are featuring Eliza Oldach. According to Ellie, “I study coastal communities, and try to understand the policies and decisions and interactions and adaptations that communities use to navigate an ever-changing world. Most of
  • by oceanbites 4 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Jiwoon Park with a little photographic help from Ryan Tabata at the University of Hawaii. When asked about her research, Jiwoon wrote “Just like we need vitamins and minerals to stay
  • by oceanbites 5 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring  @riley_henning  According to Riley, ”I am interested in studying small things that make a big impact in the ocean. Right now for my master's research at the University of San Diego,
  • by oceanbites 5 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Gabby Stedman. Gabby is interested in interested in understanding how many species of small-bodied animals there are in the deep-sea and where they live so we can better protect them from
  • by oceanbites 5 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Shawn Wang! Shawn is “an oceanographer that studies ocean conditions of the past. I use everything from microfossils to complex computer models to understand how climate has changed in the past
  • by oceanbites 5 months ago
    Today we are highlighting some of our awesome new authors for  #WriterWednesday  Today we have Daniel Speer! He says, “I am driven to investigate the interface of biology, chemistry, and physics, asking questions about how organisms or biological systems respond
  • by oceanbites 6 months ago
    Here at Oceanbites we love long-term datasets. So much happens in the ocean that sometimes it can be hard to tell if a trend is a part of a natural cycle or actually an anomaly, but as we gather more
  • by oceanbites 6 months ago
    Have you ever seen a lobster molt? Because lobsters have exoskeletons, every time they grow they have to climb out of their old shell, leaving them soft and vulnerable for a few days until their new shell hardens. Young, small
  • by oceanbites 7 months ago
    A lot of zooplankton are translucent, making it much easier to hide from predators. This juvenile mantis shrimp was almost impossible to spot floating in the water, but under a dissecting scope it’s features really come into view. See the
  • by oceanbites 7 months ago
    This is a clump of Dead Man’s Fingers, scientific name Codium fragile. It’s native to the Pacific Ocean and is invasive where I found it on the east coast of the US. It’s a bit velvety, and the coolest thing
  • by oceanbites 8 months ago
    You’ve probably heard of jellyfish, but have you heard of salps? These gelatinous sea creatures band together to form long chains, but they can also fall apart and will wash up onshore like tiny gemstones that squish. Have you seen
  • by oceanbites 9 months ago
    Check out what’s happening on a cool summer research cruise! On the  #neslter  summer transect cruise, we deployed a tow sled called the In Situ Icthyoplankton Imaging System. This can take pictures of gelatinous zooplankton (like jellyfish) that would be
  • by oceanbites 9 months ago
    Did you know horseshoe crabs have more than just two eyes? In these juveniles you can see another set in the middle of the shell. Check out our website to learn about some awesome horseshoe crab research.  #oceanbites   #plankton   #horseshoecrabs 
  • by oceanbites 9 months ago
    Feeling a bit flattened by the week? So are these summer flounder larvae. Fun fact: flounder larvae start out with their eyes set like normal fish, but as they grow one of their eyes migrates to meet the other and
WP2Social Auto Publish Powered By : XYZScripts.com