Rough-legged Hawk Light Morph
Boxing Day, December 26, 2024, dawned sunny and relatively warm, with a high of -3ºC. We had been wanting a trip to Lower Jemseg for quite some time but kept delaying it because of pre-Christmas activities. A free day, so this was the day!
The route to Jemseg and on down to Lower Jemseg makes a good birding ‘run’ this time of year. I wanted to try to see some hawks and that is the place to go - or at least it used to be. The last 2 or 3 years has changed things for this route and the hawk population in this area. In years past we would see up to 20-plus hawks on that route on a good day. I remember one day we saw 23 hawks. If you add the Bald Eagles to that sum, you get a wonderful day of birding! Well, not now. For the last two years one is lucky to see 2 or 3 hawks and many times we see none.
Our trip started with nothing and then in middle Sheffield, a fast stop for the first silhouette of a raptor in a tree. An eagle, an adult Bald Eagle. Our first raptor to record. We then drove many kilometres without seeing any other large birds. Two Common Crows were a welcome addition to our list. We scanned hundreds and hundreds of naked hardwood trees. These would have been adorned with beautifully coloured leaves just two months earlier. Now we could see deep into the forested areas because of the openness. The trees were adorned with snow, the remnants of the Christmas Eve storm.
In Lower Sheffield we saw a huge flock of Snow Buntings. Pulling over we got a good look at about 100 birds. They would land on the road covering the shoulder and half of the pavement. Quickly they would take flight and circle over the adjacent field, only to return to the road again. Fortunately, they seemed to know how to avoid the traffic.
The St. John River which runs alongside for most of the route was mostly frozen over. There were only a few mid-stream open slivers of water, not really useful for waterfowl. One of these open areas was close to shore and in it were 4 Canada Geese. They were looking quite forlorn and obviously were the remnant of the much larger flock that was using the river as a staging and feeding area on their migration south.
Periodically we saw small flocks of finches feeding on turf and soil on the sides of the road where the plough has scraped the snow off. The first few flocks we checked were of Dark-eyed Juncos, Black-capped Chickadees, and American Tree Sparrows. As we got closer to Jemseg and onto the road to Lower Jemseg, these flocks became more frequent and were mainly Snow Buntings. On the Lower Jemseg Road itself there was a late Savannah Sparrow feeding with the Snow Buntings.
Red-tailed Hawk
We arrived at the end of the road at the landing of the Jemseg/Gagetown summer ferry. A good spot to let my small dog out for a run. As we quietly stood there checking the rather large patch of open water for waterfowl, a hawk flew out of a large ash tree and sailed over our heads - a Rough-legged Hawk. Wow! I hadn’t seen a Rough-legged Hawk in 2 years. I was very excited and watched admiringly as it soared over the big open field there. It was a light morph bird. We stood around checking further and found only a few more Snow Buntings. Before we got back into the car the hawk returned to soar over again. It must have known how happy we were to see that species today!
Our trip home revealed another species, a beautiful one. As we left Turner’s Store in Jemseg a male Pileated Woodpecker flew across our view. It seemed like a nice punctuation mark to our list. The rest of our trip home did not reveal another raptor even though we scanned hundreds of hardwood trees. When we arrived home in Douglas near Fredericton, we went for a short walk in a vacant hillside area and were blessed with another hawk flying across our path. It landed in a tree overhanging the road giving me a chance to confirm its identity as a Red-tailed Hawk. It then took off and as I moved up closer to where it had disappeared, there it was sitting in full sun high up in an oak tree and facing me, its breast brilliant in the bright sun. The breast band and brown heard were easy identification features.
Winter is a wonderful time to bird. Our landscape looks empty but it is surprising what can be found. Other birds seen on this trip included Mourning Doves, European Starlings, Rock Pigeons and White-breasted Nuthatches.
Rough-legged Hawk Light Morph
What has happened to the former hawk population which wintered in the Sheffield/Jemseg area? Serious birders have been pondering that question. In Lower Jemseg this morning we stopped to talk to a retired biologist who was out on his morning walk. When asked that question his reply was wise, “Well, it certainly is not just one cause but probably a multitude of causes all working together.” He is probably right.
Maugerville, Sheffield, Jemseg, and Lower Jemseg present good habitat for raptors. Being a hardwood area over rich farmland, scrub and marsh, it provides rich feeding grounds. The rodent population must have been high there in past years. Much of the area floods each spring and I am not sure what damage that does to the rodent population. I believe a certain percentage of rodents survive in their burrows during flood waters. It is possible most of the rodent population dies out and is quickly replenished over the next year or two. Surely this has something to do with the food supply for raptors. In past years flooding did not seem to have an effect on the wintering raptor population. So, what now is the cause of the decline?
There has been a general decline in raptor populations over recent years. For example, the Sharp-shinned Hawk population has declined by 47% at some count sites. Generally speaking, causes of declines could include loss of habitat, scarcity of food resources, window strikes, predatory/prey cycles, effects of pesticides, and human disturbance. What causes are affecting the raptor population in question?
With the Sheffield/Jemseg winter population we are concerned mainly with Red-tailed Hawks, Rough-legged Hawks, and Northern Harriers. The global population of Red-tailed Hawks is estimated to be 2 million and considered stable. In fact, in recent years their numbers have increased by 1.3% per year. The Canadian population is estimated to be 500,000 to 1,000,000.
The global population of Rough-legged Hawks is estimated to be 100,000 to 1,000,000. Scientists claim this is difficult to estimated because their breeding grounds are so widespread and they have unpredictable migratory habits. However, the population of Rough-legged Hawks has been stable since the 1970s. The literature does say, however, that regional populations can fluctuate depending on the availability of prey and the weather in their breeding grounds. The main threats to the Rough-legged Hawk population are habitat loss, vehicle collisions and shooting. For example they suffer in some places from agricultural development on their wintering grounds. Vehicle collisions would be more of a cause in their wintering areas. The third important threat to their numbers is indiscriminate shooting. It is illegal to shoot hawks in New Brunswick but our game laws are sometimes poorly enforced due to low numbers of enforcement officials.
Breeding success is also a factor in hawk numbers. Research tells us that the numbers of Rough-legged Hawks in the Arctic fluctuate with the size of the rodent populations there. This is because Rough-legged Hawks are specialist predators of small mammals such as voles and lemmings. If the prey species population numbers are high, hawks produce more young and raise them more successfully increasing their population numbers.
Looking at the literature on the effects of flooding on small mammal species in the flood zone, one study from the Sacramento River found that after flooding all species declined dramatically and remained depressed for at least a year after flooding. The voles were the first species to recover. The only species that did not decline significantly were the arboreal species (squirrels). The same study also found that the vole populations declined as agriculture sites became more mature.
A study done in Albuquerque, NM, found that after annual flooding there was no clear effect of flooding on the density of small mammals. They found that some mice used trees as refugia during the floods. Another study found the highest numbers of small mammals on and near the non-flooded elevated parts of the area. Another study confirmed this and found that flooding was not detrimental to the rodent numbers. Another study done at Dongting Lake in China where frequent flooding occurred found that there was a significant decrease in rodent populations after a long period of flooding compared to a short period. They found that the rodent population increased rapidly after the flood and became greater than the unflooded areas in half a year.
So what does this mean about the Sheffield/Jemseg site? The winter population of Rough-legged Hawks is presently very low in this area. This is not the case in other parts of New Brunswick. A recent report from the Tantramar area reported 16 Rough-legged Hawks sighted in one day. Are we looking at two different populations here? One population might be migrating down the east coast and wintering at Tantramar. Another population (now very low) might migrate down the St. John River to winter in the Sheffield/Jemseg area. Perhaps some of this population has changed its route to the east coast. Or perhaps the breeding success on the St. John River population was much lower than the east coast population.
Has there been a change in habitat? It does not appear that there has been significant changes in agriculture in the area. It might be possible that a new/different agricultural chemical is being applied to the land. There may be less acreage under cultivation. This might make some of the former heavily populated rodent sites too mature and thus support a smaller population. The number and duration of the floods might also play a part. We seem to have fewer heavy floods now (speculation) so that might have an effect. An argument against that is that the population seemed to be stable for many years and the floods probably fluctuated during that time with no appreciable change in hawk populations. Or, no flood at all as happened in 2024? One study mentioned above found that the populations became greater after flooding so perhaps no flooding is a detrimental effect. And lastly, what about the breeding grounds? If the population of rodents on the breeding grounds was low or the weather bad or the predator populations high, these factors could affect the breeding success.
The biologist we discussed this issue with was right! There must be many factors causing the decline in the wintering population of hawks in the Sheffield/Jemseg area. We need more information. A study of this problem might help us improve the St. John River wintering hawk populations.
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