June 23rd 2014, PAJA Pair 2

I was finally able to spend a longer period of time observing the second pair of PAJA almost a week ago. They defended against me at 78 meters from their nest. They defended against another PAJA, a Common Raven and many Glaucous Gulls.

PAJA Pair 2             Date: 6/23/14           Time spent observing: 16:16 – 17:46

Temperature: 55 F    Wind 17 mph          50% Cloud Cover

Type of Behavior	Total Time Dark Morph	Percent time spent doing behavior	Total Time Light Morph	Percent time spent doing behavior
Defending	10	11.11	13	14.44
Incubating	60	66.67	17	18.89
Hunting/Foraging	7	7.78	2	2.22
Preening	2	2.22	35	38.9
Loafing	11	12.22	21	23.33
In flight	0	0	1	1.11
Altercation	0	0	1*	1.11

Total time spent observing: 90 minutes

* = Listed a seemingly defensive attack on a Snowy Owl as an altercation because the owl was loafing on the tundra over 200m from nest when the jaeger flew over to and harassed the owl.  

We will be pretty busy in the next week, so I will probably not have much time to observe either pair. But for now, please enjoy this video of PAJA Pair 2 defending their nest against me. It was a windy day and a lot of the "squeaks" are obscured by the sound of wind. So you may want to turn your speakers down to a reasonable level.

Questions

Since beginning these observations, and even before, I have had a lot of questions about the behavior of these birds running through my head. For now I will hash them out and later see if I can sort of narrow it to one.

1.) The first that I thought of, whether or not these birds are capable of recognizing individuals other than intraspecifically (I may have made that up). It has become clear to me PAJA Pair 1 are more defensive each year I have worked here. I think they are capable, like corvids and some terns, of recognizing individual observers, especially those that have disturbed them in some way. Thence, recognizing those individuals and behaving more, or in some cases, less aggressively.

2.) Another, and one I have loosely tested in my observations, is a question of how close to a nest can a potential predator or observer be, for the birds to begin defensive behaviors. Also, does the distance increase the closer the eggs are to hatching or the adults are brood-rearing? Additionally, do the defensive behaviors become more aggressive depending on if they have a full clutch (2 eggs) versus a single egg (as may also be the case with Pair 1's extreme aggressiveness compared to Pair 2)?

3.) In all of the literature I have read, it appears that it is more common (61% of birds measured) for males to be dark-mophs. I question if this is the case with breeding populations here with my own observations of Pair 1 over the years. As I have mentioned before, I believe the dark-morph of this pair is larger than the intermediate (as females are larger) and it was the primary attending parent when the chicks had hatched in previous years. There really is no way to test this unless I was to be on a project studying these birds by trapping and getting measurements and blood samples. But, when the eggs do hatch, it might be possible to observe the brood-rearing behavior to get a feasible idea.

4.) Just through some of my recent observations, and to coincide with the first question, what constitutes a potential threat or predator to these birds, and if they recognize those that are not worth spending their time and energy to defend against. Along with, is there a distance the potential threat has to be in proximity to the nest for the bird(s) to initiate defensive behaviors?

Again, throwing these out there mostly so I can think about them more, and how each could possibly be tested and answered.

June 21st 2014, PAJA Pair 1

I spent some more time with PAJA Pair 1 on the 21st and below is a table of the behaviors observed. The pair began defending against I and my team member at a distance of 90 meters from their nest. I was able to sit and observe them for awhile at 83 meters from the nest until about 15:33 when the dark-morph was loafing and then saw me and chased me off. I then observed them from 109 meters.

This time around the pair also defended against a Glaucous Gull which I had previously seen them ignore once. 

PAJA Pair 1               Date: 6/21/14             Time spent observing: 14:50 – 16:10

Temperature: 35 F      Wind 15 mph            100% Cloud Cover

Type of Behavior	Total Time Dark Morph	Percent time spent doing behavior	Total Time Intermediate Morph	Percent time spent doing behavior
Defending	9	11.25	2	2.5
Incubating	35	43.75	40	50
Hunting/Foraging	0	0	0	0
Preening	4	5	13	16.25
Loafing	29	36.25	24	30
In flight	1	1.25	0	0
Altercation	2*	2.5	1**	1.25

Total time spent observing: 80 minutes
* = Listed an interaction with another dark-morph PAJA as altercation, because did not clearly defend. Interaction actually appeared to be more 'friendly', since after initial interaction, they both stood on the tundra within a few meters of each other.

** = Altercation was with a pair of King Eiders, may have been harassing them if there was a nest, but I did not check if was the case.

I realize that the tables are extending beyond the bounds of the post and I am trying to fix it. I apologize if it makes it a bit more difficult to read. **EDIT: I fixed them! 

PAJA Predation Events

Since I discussed a little bit about a possible third pair and the artificial nest project, I figured I would share a few pictures the Reconyx cameras capture of the predation events.

Again, one of the projects I am working on involves setting out 60 artificial nests on a road transect that goes away from a "hub" of infrastructure. It is testing whether or not those predators considered to be subsidized by humans (Red Foxes, Glaucous Gulls, Common Ravens) are preying on nests closer to the infrastructure. The artificial nests are made with quail eggs for shorebird nests, and Mallard eggs for duck nests. We have seven Reconyx cameras that we set on artificial shorebird nests that are chosen randomly. Parasitic Jaegers are not considered to be subsidized predators, yet, it is possible that this pair has learned that the cameras provide an easy meal, and have since depredated all of our nests. Well, at least we know of three that they were caught on camera.

PAJA has spotted nest and comes in for landing.

I really like the above shot, mostly because it shows how agile and acrobatic these birds are. 

Mate comes in to investigate. Other has quail egg in bill.

Light morph takes a quail egg.

Just another nice flight/landing shot.

Two hours later, pair goes to other artificial nest. 

In this picture you can see that it has already swallowed one or more eggs, stored in the crop, and is taking another. 

I find these interesting, mostly because I have not seen that much feeding behavior in the pairs that I have been observing. It seems like they may actually forage together, or maybe in the case of one of our nests, it was near enough to their nest that they both flew over. I have read in the Birds of North America species account for PAJA, that pairs often hunt together, except when incubating. Also, when they are feeding chicks, they will often leave it unguarded to hunt together. I think it will be interesting to see if they behave this way if and when their eggs hatch.  

I have a couple of observations of both pairs that I have to post and will also write out some of my questions in the next couple of days, so stay tuned! 

Pair 2 Observations

On the 19th, we were planning to do our surveys on the sites that are furthest west from our home base. However, due to bears in two of the areas where those sites are located, we were forced to take a shorter day. I was hoping to get some more time in on PAJA Pair 2, since I was only able to observe them for a short time the last time, but I only got another 36 minutes in.

Light-morph of PAJA Pair 2

So, I used the time more to test some ideas about how close I can approach the nest before they defend against me. I was 66 meters away before they began to defend. With PAJA Pair 1, on the previous observation, I was 100 meters away when they began their defense against me. I also noticed with Pair 2 this time and the first observation, that I walked away a mere 30 meters when they returned to incubating the nest. I believe this may be due to the current weather conditions. Almost every day has been in the low-mid 30s (Fahrenheit) and with 10-14 mph winds each day. I have actually noticed a few species of tundra nesting birds doing this, including American Golden-Plovers which typically do not go back to their nests with a predator so close.

Here is another chart of my observations for the day.

PAJA Pair 2                Date: 6/19/14              Time spent observing: 14:00 – 14:36

Temperature: 34 F      Wind 10 mph      100% Cloud Cover

Type of Behavior	Total Time Dark Morph	Percent time spent doing behavior	Total Time Light Morph	Percent time spent doing behavior
Defending	7	19.44	4	11.11
Incubating	6	16.67	22	61.11
Hunting/Foraging	0	0	1	2.78
Preening	1	2.78	1	2.78
Loafing	20	55.55	5	13.88
In flight	1	2.78	1	2.78
Altercation	1	2.78	2	5.56

Total time spent observing: 36 minutes 

Day One

On the 16th I was able to spend some time with both pairs of Parasitic Jaegers. I located both nests in the same day, and based on their behavior previous visits, I can estimate within a week when the eggs should be hatching. I will from now on refer to them by their AOU code, PAJA. It makes writing a bit easier. 

I first spent some time with the second pair, which I previously said I probably would not get as much time to observe. However, I think discovering that one pair has a full clutch of two eggs (Pair 2) and the other only has one egg (Pair 1), that I will try (time permitting) to observe both equally. For this first observation though, I only spent enough time to find Pair 2's nest and observe them briefly. 

Behaviors are defined as below.

Defending – defending nest/brood from potential predators, including observers. It also defines the “broken-wing” display defense

Incubating – sitting on nest, incubating egg

Hunting/Foraging – actively flying in search for prey/food item, defined by bird in flight and scanning ground or hovering in one place above prey/food item. If one bird leaves area and is out of sight of observer, it is assumed they are hunting/foraging until they are seen again

Preening – preening feathers, bathing in water

Loafing – standing/sitting on tundra with no apparent purpose

In flight – in air flying with no apparent purpose

Brood – attending brood/young

Altercation – with other bird that is not explicitly due to defending of nest/brood

PAJA Pair 2            Date: 6/16/14            Time of observation: 9:50 - 10:25

Temperature: 34 F    Wind at 11-27 knots   Light fog

Type of Behavior	Total Time Dark Morph	Percent time spent doing behavior	Total Time Light Morph	Percent time spent doing behavior
Defending	15	42.86	9	25.71
Incubating	2	5.71	24	68.57
Hunting/Foraging	0	0	0	0
Preening	0	0	0	0
Loafing	15	42.86	2	5.71
In flight	0	0	0	0
Altercation	3	8.57	0	0

Total time spent observing: 35 minutes

I made this kind of chart for both pairs, although since my time was so brief with Pair 2, it really could not be used for much scientific analysis. This pair defended against me obviously. I think also because it was quite cold, that they went back to incubating when I was still within 40m of the nest. They also defended against a Common Raven and Glaucous Gull. The dark-morph of this pair chased away a pair of Canada Geese and Greater White-fronted Geese, apparently for no reason at all.

PAJA Pair 2 nest with two eggs

Dark morph of PAJA Pair 2

 

PAJA Pair 1              Date: 6/16/14                 Time of observation: 13:35 - 15:01

Temperature: 34  F    Wind at 11-27 knots    Sun shining

Type of Behavior	Total Time Dark Morph	Percent time spent doing behavior	Total Time Intermediate Morph	Percent time spent doing behavior
Defending	15	17.44	16	18.6
Incubating	50	58.14	20	23.26
Hunting/Foraging	4	4.65	8	9.3
Preening	8	9.3	18	20.93
Loafing	8	9.3	21	24.42
In flight	1	1.16	1	1.16
Altercation	0	0	2	2.33

Total time spent observing: 86 minutes

This pair has gotten even feistier; I didn't even try to get pictures of their nest because of their incessant dive-bombing. They only have one egg, and may be more defensive as a consequence. They defended against another PAJA, as well as a Pomarine Jaeger. I may not have mentioned this before, but the previous two years I was here, I only saw Pomarine Jaegers in the beginning of the summer. They are a species that is highly dependent on lemming populations as a food source. Although we have not seen many lemmings, they are sticking around, and we have even found a nest near some of our study plots. 

I also observed a Long-tailed Jaeger, a Glaucous Gull and a Short-eared Owl fly by the pair, but they did not defend against any. Again, begging the question, if they are capable of recognizing individuals of different species so that they do not invest time and energy in defending when the bird flying by is not a threat.  

I am hesitant to say that the dark morph in both pairs is the female based on what I have read about polymorphism being attributed to sexual selection in these jaegers. However, they also exhibit reversed sexual dimorphism, where the female is larger than the male, and I am positive that PAJA Pair 1's dark- morph is larger than the intermediate-morph. Plus, I would assume that the female incubates for a longer period of time, and the dark-morph was incubating for 50 minutes, 58% of the time that they were observed. Also, in previous year's the dark-morph has been the primary parent attending the brood. So, I guess I will see if there is more information on this, and try to have a better idea of which individual is which.

Parasitic Jaeger Life History

I decided, before I delve too much into these field observations that I should provide some background on the life history of this species, so here it goes.

Parasitic Jaeger, Stercorarius parasiticus

aka Arctic Skua or Parasitic Skua (American Ornithologists' Union code: PAJA)

Order: Charadriiformes

Family: Stercorariidae

Parasitic Jaegers are fast-flying and agile seabirds. There are two color morphs and an intermediate color morph between the two. The light-morph adults will have a brown back and mainly white underparts with a yellowish white on the head and a black or brown cap. Dark-morphs are dark brown all over and the intermediate-morph birds can be brown with some lighter brown or dusky white on the head. The Parasitic Jaeger has two central tail feathers that stream out and come to a point up to 7 cm from the edge of the other tail feathers. A Long-tailed Jaeger has much longer central tail feathers (15-16 cm) and a Pomarine Jaeger's two tail feathers are kind of spoon shaped.

They breed on tundra in Alaska, Northern Canada and Northern Eurasia; and winter in the oceans of the Southern Hemisphere. On the breeding grounds they feed on rodents, small birds, eggs, insects and even berries. In the winter time they obtain food by pursuing gulls and terns and forcing them to drop their food, again showing off their agility in flight. This is called kleptoparasitism, which may also be a reason for their name.

Pairs generally return to the same breeding territory each year, that site fidelity we have noticed. They typically lay two olive-brown eggs on a grassy depression on the tundra. I have noticed that they like to stand on higher mounds of dry tundra, but nest on ridges or small mounds that are surrounded by a wetter tundra. Through doing these field notes, I have also discovered that pairs are bi-parental, meaning they will both incubate the eggs. The incubation period is 25-28 days. The young will stay with the parents for a few weeks after fledging.

I was able to observe both pairs earlier today, and will be writing a summary of those notes tomorrow if I get the chance. I have also considered adding a third pair, if I can find their nesting territory. Part of the project I am working on is to set out artificial nests with real eggs, quail eggs to mimic shorebird nests, and monitor them as if they are real nests. We then use a few cameras to try to capture predators that come to the nests. On our most recent check, we had three camera nest predation events, and each was depredated by a PAJA pair at different time intervals. Meaning they probably have a nest nearby and have probably cued in on the cameras and getting a free meal. So, I would like to find out where they are, especially since it would be a pair that has been previously unexposed to my presence and could provide some interesting observations as far as defensive behavior.

Why this species?

I have created this blog in accordance with the field notes assignment for the Animal Behavior MOOC offered via Coursera by Raoul Mulder and Mark Elga of the University of Melbourne.

I have worked in the Arctic for the past three summers for Wildlife Conservation Society on a Pad Rehabilitation study in collaboration with BP within the oilfields of Prudhoe Bay, Alaska. I have observed two Parasitic Jaeger pairs nesting in the same areas these past years. Both pairs are back again this year, and taking this class, I realize that this might be a good species to do a field journal on.

Aside from apparently having site fidelity, these birds are some of my favorite tundra nesting species. They are superb fliers and predators, and are very defensive parents. I also suspect they are able to recognize individuals, for example, I have noticed they are more defensive when I am present than when another crew member is present. Again, this is my third summer here, and only the first for the other crew members, so I am interested in seeing if they "remember" me and hence defend against me more than a "stranger." I will describe the two separate pairs as Pair 1 and Pair 2. Pair 1 is the pair I am very familiar with and hope to get some interesting data from them and Pair 2 is the pair that will be used more for general observations. Please keep in mind that I am also working while completing these observations and most may be very brief, but I will try my best.

Dark morph Parasitic Jaeger from Pair 2, July 2013

If you are interested, I have another blog (specifically this post about my first enchantment with the Jaegers) where I have discussed more of the work I have done here. I told myself I wouldn't come back this year after the last and even the year before that, but here I am. The Arctic and the Arctic Coastal Plain specifically, is an amazing place and has sunk it's tendrils deep in my heart, drawing me back for this (I won't say last) summer. And yes, my background image is actually a Long-tailed Jaeger, I wanted to use it since it is one of the best pictures I have of any of the Jaegers here.