Feeds:
Posts
Comments

Archive for the ‘Behavior’ Category

Mute Swans (Cygnus olor) are a species that is growing more and more numerous, and this is a problem.

Mute Swans are the “classic” swan from stories and art. They are large and showy and beautiful and these traits are exactly why they have been introduced to North America. Birds were brought from Europe in the 1800s and released in parks, gardens, etc. as ornamental additions (New York was the original release area). These birds have since reproduced and spread across the continent as far north as New Hampshire, as far south as Florida, and as far as west as California.

Adult male Mute Swan (Cygnus olor). Source: USFWS digital library.

They are becoming problematic for several reasons. One is that they are quite aggressive, and will chase and bite humans if that human trespasses on the swan’s territory. Another is that they consume quite a bit of food. They are big birds reaching up to 25 to 30 pounds, and that means they eat about eight pounds of aquatic vegetation every day. That is food which is then not available to native birds, and it disrupts habitat for native birds, mammals, fish, and other species. And a third reason is that the swans are directly aggressive to other species of bird driving them off nests, breaking eggs, and killing the chicks of other species, and so displacing those other species from areas where they would otherwise live. With habitats becoming ever smaller and more fragmented, this can mean the native species can be left with no where to go.

These problems have all contributed to Mute Swans being added to California’s restricted species list in 2008. This listing means the birds cannot be imported, transported, or possessed in the state without a permit. This has not completely prevented the swans from beginning to become established in California. Small populations can be found in Petaluma and the Suisun Marsh. I suggest that removing this species while the population is still small is the best course of action. There is every reason to suspect that the population will grow, and as it does so, the problems listed above will become more and more apparent. However, control will become more and more difficult.

One interesting thing about Mute Swans in North America is that they do not migrate very much. There are certainly some, relatively short, seasonal movements that occur in some parts of the continent, but not much. Certainly nothing compared to the long migrations that Mute Swans in Europe engage in. The evolution of this behavior in a novel environment illustrates how different geographic regions can cause a species to adapt and change. This behavioral evolution could then lead to the evolution of a new species, if it persists and becomes dramatic enough.

So, what can you do to help native birds and habitats, and prevent Mute Swans from taking over? If you spot a Mute Swan in California, contact the California Department of Fish and Wildlife – Invasive Species Program by sending an email to: invasives@wildlife.ca.gov or calling 886-440-9530. Together, we can act as citizen scientists to gather data that tracks where these birds are and how they move around. This data will help us all make the best and most informed decisions we can about this species.

Thanks for visiting my blog. If you are interested in other ways to connect with me, here are a couple of options:

YouTube – A Birding Naturalist

Instagram – abirdingnaturalist

Read Full Post »

Have you ever seen a v-shaped flock of geese fly overhead and wondered, why do they do that? In this video I share some information explaining this interesting behavior. I also talk about the other species that also fly in v-shaped flocks, and dispel an oft repeated myth.

If you enjoy the videos I am creating, two ways to stay informed would be to subscribe to the A Birding Naturalist channel and/or become a follower of this blog.

Eurasian Cranes (Grus grus) flying a v-formation (Photo courtesy of Wikipedia)

Read Full Post »

A few years ago I wrote a post on niche partitioning among herons and egrets. That post was inspired by watching several species of herons and egrets foraging for food along Putah Creek near Davis, CA, and the resource they were partitioning into niches was food.

Recently, as part of my work at the Sacramento-San Joaquin Delta Conservancy, I encountered another example of niche partitioning by herons and egrets. This time, the resource these birds are partitioning into niches is nesting trees.

One of the grants that I manage at the Delta Conservancy is at the Cosumnes River Preserve and it includes and grove of large Valley Oak trees that many herons, egrets, and cormorants use as a rookery (a rookery is a colony of breeding animals, generally birds). One way that the various species have evolved to utilize the same trees, and yet avoid directly competing with each other, is for each species to utilize a different part of each tree to nest in.

Great Blue Herons typically nest on the very tops of the crowns of trees, Great Egrets typically nest only in the upper one-third of the canopy, Snowy Egrets typically nest in the middle one-third of the canopy, and Black-crowned Night-Herons prefer to nest in the lower one-third of the canopy (see the image below).

Niche partitioning of nesting locations within a tree by heron and egret species

I think this stratifying of nesting locations is amazing! Species have evolved to fill so many different niches, and so many niches can be divided into finer and finer gradations. I wonder if there is really any limit to how many species can evolve, and how complex an ecosystem can develop, in a give location.

Read Full Post »

Homosexuality has been observed is just about every species it has been looked for. Transgender animals are not as widely known, but may just be a matter of looking for them.

There are certainly some animal examples that are various forms of transgender animals in nature. One is the California Sheephead (Semicossyphus pulcher) which is a fish that is born female, and then can become male later in life. Another example is found in the Green Frog (Rana clamitans) that reverse sex in response to various external factors, and this has been observed in other amphibians as well. But both of these examples are in lineages of animals that are pretty distantly related to us humans.

lionesses-with-manes

Photo of two lions one is male sex (left), one is female sex (right), but both display male characteristics.

Well, research published a couple of years ago in the African Journal of Ecology is an example much closer to us. In a paper by Gilfillan et al. from the University of Sussex, five lionesses in Botswana have been observed to grow manes, regularly roar and scent mark, mount other females, and display other very male-like behaviors such as killing the cubs of rival prides which females lions just about never do but is very common for male lions.

This is a mammal we are talking about.

Lions that are female in body, but male in behavior.

In the wild.

Still think being transgender is unnatural?

Transgender Flag

Read Full Post »

My wife, daughter and I were in Berkeley, CA this weekend visiting my mom and some friends. One morning, while we were having breakfast and watching the visitor to the bird feeders hanging not far from the floor-to-ceiling windows, we witnessed a pretty dramatic event.

PUFI

A female or juvenile Purple Finch.

As we eat our breakfast, a group of three or four Purple Finches were enjoying their’s. Suddenly, a California Scrub-Jay made an ambush attach on the feeder! It flew in through the branches of the Incense Cedar, and startled the finches into a bit of a panic. One of the Purple Finches (either a female of juvenile bird) made a very bad decision, and flew directly away from the incoming jay which meant it crashed into the big windows right in front of us. The jay flew past the feeder, not stopping at all, and landed on a table near the big windows. It seemed from watching the flight of the jay, that landing on the table had been its plan. The finch was on the deck, stunned by the impact with the window. The jay looked down, watched the finch for a moment to assess its condition, and then jumped down, grabbed the adult finch in its beak and flew away toward a large tree that we are pretty sure this bird and its mate have a nest in! That’s right, as if it was pretending to be one of the small hawks or falcons, the jay picked up the stunned Purple Finch and flew off with it!

CASJ

California Scrub-Jay

This whole event only took a total of about one minute, but it got us all talking and thinking a fair bit about what we had just seen. First off, What a sight to see! All of us around our breakfast table were pretty surprised, impressed, and a few were taken aback at seeing a predator prey interaction at such close range. Secondly, I have never seen a California Scrub Jay prey on an adult songbird, before! I looked it up, and while there are reports of similar behaviors, they are not common. Thirdly, was driving a finch into the window the jay’s plan? The jay seemed like it was aware of the window, as its movements never put it in any danger of colliding itself. The finch was either unaware of the window, or was so frightened by the jay’s sudden attack that it forgot about it. So, did the jay basically hunt the Purple Finch using a window? Jays, members of the corvid family along with ravens, crows, magpies, and others, are highly intelligent and have been observed using tools in a range of settings. So, using a tool such as a known window location to incapacitate prey certainly seems possible.

Regardless of whether or not the window was used as a hunting tool, or if the jay just got lucky, this was a pretty impressive sight to see. And those baby jays had a very big breakfast of their own that morning!

Read Full Post »

Information is important. With information each of us as individuals, and our society as a whole, can learn about the world. With information, we can all make decisions that make sense. With information, we can all discuss ideas.

Without information none of that is possible. Without information, we are, at best, at the mercy of our current, limited knowledge, and our base instincts. Without information we are, at worst, at the mercy of the limited knowledge and instincts of someone else.

This is why the gag order, and insistence that all reports and data be pre-screened before release to the public, issued by the President to the EPA are so concerning to me, and I think should be so concerning everyone else. This is exactly the kind of action that limits access to, and spread of, information. It will only hamper all of our abilities to operate as rational, critically thinking individuals. It is the kind of action that is put in place to control what we, as citizens, know and when we know it. This is censorship and it has no place in science or a free society.

#thisisnotnormal

pansy-white-blue

Read Full Post »

I have written about the conflict between Spotted Owls (Strix occidentalis) and Barred Owls (Strix varia) a couple of times before (here and here). The basic situation is that Barred Owls (generally native to eastern North America) have been expanding their range into the range of the Spotted Owl (western North America) for the past 40 years or so. The Spotted Owl has been declining for a long time and two of the three subspecies are federally listed as Threatened under the U.S. Endangered Species Act. The intrusion of Barred Owls is now a big problem for the Spotted Owls for several reasons.

Spotted Owl - USFWS

A subadult Spotted Owl (photo by USF&WS)

One reason is that the total Spotted Owl population is smaller than the total Barred Owl Population, and small populations are more at risk of declines and extinction. Another reasons is that the Barred Owls are bigger and more aggressive than Spotted Owls and push the Spotted Owls out of nesting territories. Sometimes the Barred Owls are big enough and aggressive enough that they eat the Spotted Owl. Yet another issue is that the two species of owl are so closely related that they can hybridize and produce so called Sparred Owls. This genetic mixing has much more profound implications for the long term persistence of the Spotted Owl than the Barred Owl due the much smaller population size of the the former.

The primary solution that has been proposed to save the Spotted Owl from extinction has been to alter logging practices and set aside the old-growth forests that the Spotted Owls depend on. However, this has not been enough to halt the Spotted Owl decline. An additional plan that the U.S. Fish & Wildlife Service has been pursuing is the lethal removal of Barred Owls from areas where Spotted Owls are nesting or have nested in the recent past. From 2009 to 2013, USF&WS scientists killed approximately 90 Barred Owls. This had a marked effect on the Spotted Owl population. In areas where Barred Owls were removed, Spotted Owl population levels did not change any more than in areas where Barred Owls had never been observed. Also, territories that were held by the removed Barred Owls were fairly quickly re-occupied by Spotted Owls.

This result is a surprise to me. In my past posts, I was quite critical of the plan, and was skeptical that the removal of Barred Owls would actually benefit Spotted Owls. The results of the removal study suggest that this strategy might work to preserve Spotted Owls. But there are still problems.

barred_owl_ashley_hackenberry

An adult Barred Owl (photo by Ashley Hockenberry)

Spotted Owls respond well to the removal of their Barred Owl competitors. But how will these removals be maintained? Shooting Barred Owls takes a fairly considerable effort, so there is no way that this process can be enacted over the whole range of the Spotted Owl. It will not be possible to even do it over large areas. Instead, the only way that this plan will be able to be put into practice will be on very small areas of core Spotted Owl habitat. The other problem is one of time. To be effective, these core areas will have to be patrolled regularly, forever. New Barred Owls are perfectly capable of re-invading areas where the earlier Barred Owl inhabitants had been shot, and they will do so in short order.

So, much of my skepticism and critiques from my earlier posts still stand. I do not think that killing Barred Owls is a long-term solution for Spotted Owls on really any scale that will be useful for the survival of the species. It will simply require more time, effort, and money than anyone has to devote to the issue. That having been said, the fact that killing Barred Owls made any impact on Spotted Owls at all is more than I thought would happen.

Read Full Post »

A post from AbirdingNaturalist has been accepted to the website NatureWriting! With the acceptance of my piece titled “A Vomiting Vulture,” I am now a contributor. This is the first time one of my posts has been featured on another website, so I am pretty excited!

NatureWriting can be found here.

My post can be found here.

Check them out!

Read Full Post »

OR_25 May 20 2014_Imnaha PackAllow me to introduce you to OR-25, the most recent wolf visitor to the great state of California. This very handsome 3-year-old fellow recently left his Imnaha Pack in eastern Oregon. He decided to walk south and, just last week, crossed into California where he has been hanging out in Modoc County. His arrival, along with OR-7 who visited for most of 2012 before settling just north of the California/Oregon border to have babies and the Shasta Pack that has established itself in Siskiyou County in 2015, may indicate that wolves are starting a trend of dispersal and range expansion into this state. If this expansion continues, we who live in California may be lucky enough to encounter these long-lost members of our state’s wilderness. I am certainly hoping for it!

Read Full Post »

As part of my current job with the California Department of Water Resources, I assist in collecting data for a study that is monitoring predators in the Clifton Court Forebay (CCF). The CCF is where water is collected and then pumped into the California Aqueduct for transport to southern California. One of the challenges to providing water to southern California is that there are several threatened or endangered species that live in the delta. Fish that get sucked into the pumps of the aqueduct do not survive, so keeping state and federally list species out of the system is important. The study I have been working on the past four months is examining threats to the listed species. One component of that study is to catch predatory fish such as Stripped Bass (Morone saxatilis), Largemouth Bass (Micropterus salmoides), and several species of Catfish (Ictalurus spp. or Ameiurus spp.). Once captured, these fish are tagged with little transmitters that send out signals that can be detected by underwater microphones, called hydrophones, that are setup throughout the area. By tracking when and where these predatory fish go, we hope to be able to figure out a way to reduce the number that come into CCF and eat the listed species.

Fall-run Chinook Salmon

Fall-run Chinook Salmon

One of the listed species we are concerned with are Chinook Salmon (Oncorhynchus tshawytscha), and I got an up close and personal look at one just a few days ago. As the team I was a part of was fishing in CCF, I got a hit on the lure I was using. It felt like a brick had been dropped on my line as the fish swam away from me and the boat. As I worked to real the fish in, everyone on the boat was getting curious to see what species I had hooked, just how big it was going to end up being. When I had finally pulled the fish to the surface, we were all really surprised to see that it was a Chinook! We are not supposed to catch salmon, and generally they do not attack the lures we use, additionally salmon at this time of year are not really eating but are instead focused on finding a mate and spawning. So this really was a surprise! When we got it on board to get the hook out of its mouth we quickly measured it (61 cm), weighted it (6.55 lbs), and got it back in the water so that it could go on its way.

Getting to see this fish, the largest fish I have ever caught, to hold it and then to watch it return to the water got me thinking a lot about Chinook Salmon. I am starting a new job on Monday which will focus on restoring many areas of the delta, and listed species will be a large part of those projects, so I figured that learning a bit more about salmon would be a good idea.

It turns out that there are four different runs of salmon that move through the California Delta. The different runs are defined according to when the different populations enter freshwater as they travel up from the Ocean and San Francisco Bay through the Delta and up the various rivers of California. The four runs are the Central Valley Fall-run, the Central Valley Late Fall-run, the Sacramento River Winter-run, and the Central Valley Spring-run. Each of these runs are considered to be evolutionarily significant units and so are monitored and managed for their specific needs.

Central Valley Fall-run Chinook, like the one I caught, are the most abundant of the four runs. They move through the area from July to December and spawn from early October through December. There is a fair bit of variability from stream to stream. Fall-run Chinook are an important economic factor due to the large numbers that are caught by both commercial and recreational fisheries in the ocean and by recreational anglers  once they reach freshwater. Even so, due to concerns about population size and the influence of hatchery-raised Chinook, this run is listed as a species of concern under the federal endangered species act.

Central Valley Late Fall-run Chinook migrate into the river systems from mid-October through December and spawn from January through mid-April. Again, due to concerns about population size and the influence of hatchery-raised Chinook, this run is listed as a species of concern under the federal endangered species act.

Sacramento River Winter-run Chinook pass through the Golden Gate from November through May and then move into the Sacramento River from December all the way through early August. They then swim up the mainstem of the Sacramento River to spawn from mid-April through August. These salmon used to go farther up the Sacramento River watershed and spawn in the McCloud River, the Pit River, and the Little Sacramento River. However, the construction of several dams have not blocked access to these historical spawning grounds. Despite these dams, the population of Sacramento River Winter-run Chinook was able to maintain a fairly healthy level until the 1970s when they began to decline. By the early 1990s only about 200 spawning salmon were observed. In 1989 this run was listed as endangered under the California Endangered Species Act and they were then listed as endangered under the federal Endangered Species Act in 1994.

Central Valley Spring-run Chinook begin moving up the Sacramento River from March through September. They generally the find areas of cold water to wait out the summer and then spawn from mid-August through October. This run used to be the largest in central California however, only small remnant populations are left in small creeks that make up some of the tributaries of the Sacramento River. Some Spring-run Chinook still occur in the mainstem of the Sacramento and Feather Rivers, but they sometimes hybridize with Fall-run Chinook. The reduced spawning areas, small population size, and hybridization threat lead the Central Valley Spring-run Chinook to be listed as threatened under both the federal and California Endangered Species Acts in 1999.

So, there you have them, the four Chinook Salmon runs of the California Delta. There are many other runs in other parts of the state, all with their own unique stories and histories. It will be interesting to see how I will be interacting with these runs in the habitat restoration work I will be doing. I will keep you informed!

Read Full Post »

Older Posts »