Young male Sharp-shinned Hawk – our second of the season.
The neat thing about volunteers is that they bring their own unique interests and talents with them and, in so doing, enrich the overall program. Here’s an example – a convoluted one but a good one:
Lisa Horn first visited the banding program in the Spring while enrolled in Dave Jolly’s ecology courses. She found that she really liked the bird banding aspect of the course and so, dragging partner Raffaele with her, decided to come out regularly on weekends to continue learning. This past Saturday we were talking about the connection between bird numbers and fruit crops at Ruthven. And I wondered out loud what the nutritional makeup was of the various fruit we have here. And I said to her: “Look, if you don’t have anything to do in your spare time, why don’t you try to find out about this.” Now, I tend to throw these ideas out with great regularity (I’m an ideas guy after all) but not many people take me up on them. So I was very pleasantly surprised when I got her email:
Hi Rick, I had a chance to look into your question about the nutritional content of grey dogwood berries and wild grapes. In short, the answer is that grey dogwood is 33.5% lipids and 22.1% carbs, and wild grapes (Vitis sp.) are 47% carbs and 2% lipids.
I learned some interesting things that you may or may not already know (although it appears that there is not really a firm consensus on any of this information as there isn’t a huge body of literature surrounding it). Apparently Nearctic thrushes and yellow-rumped warblers generally consume low-sugar, high-lipid fruits, while cedar waxwings specialize on high-sugar, low-lipid fruits. Consumption of high-lipid fruits by birds capable of efficiently digesting them (because apparently not all birds can) may facilitate the accumulation of fat stores (Zurovchak, 1999).
Robins and catbirds can’t digest sucrose, but they eat grapes as much as cedar waxwings. Apparently eating insect protein along with the fruits can help remedy the situation. This study also found that birds increased their use of habitats as fruit resources increased (Suthers et al, 2000).
Another study (Mudrzynski et al, 2013) found that migrants and fall residents preferred mid-successional shrublands with a variety of fruiting shrub species. Catbird presence was positively related to fruiting shrub species richness, robins were positively related to total shrub cover and fruit abundance on common buckthorn, and song sparrows were positively related to the presence of grey dogwood. An interesting finding of this study was that they found that birds avoided native dogwoods and consumed more exotics like bella honeysuckle and common buckthorn.
I’ve attached the studies in case you were interested. If there’s anything else you’d like information on, let me know and I’ll try to dig into it!
Lisa
[If anyone would like PDF’s of the studies mentioned email me and I will send them.]
A family of Eastern Bluebirds checking out the Purple Martin setup.
Young male (left) and female Eastern Bluebirds.
Right now many species are eating fruit, especially grapes. Our hands are purple by the end of the day from handling the defecating little blighters. Today these included Downy and Hairy Woodpeckers, Nuthatches, Eastern Bluebirds and Robins, Gray Catbirds and Cedar Waxwings, Song and White-throated Sparrows. The consumption of dogwood berries doesn’t leave such a noticeable mark but I’ve been surprised at some of the species I’ve seen eating them, including insectivores like Red-eyed Vireos and Eastern Wood Pewees.
As I mentioned in yesterday’s blog, the number of birds that we’ve been catching is down. This is especially noticeable in regard to some of the fruit eaters – Cedar Waxwings in particular. This would seem to be related to a fairly meagre fruit/grape crop (when compared to last year). I guess my next question would be: how do birds know when an area has a good crop? After all, they migrate at night at around 300+ meters. How do they sense what is below them? Passerines aren’t supposed to have much of a sense of smell. But are they able to pick up certain chemical compounds given off by the fruit? Please feel free to weigh in on this question…..
Blue-headed Vireo
Western Palm Warbler – maybe on its way to Cuba.
Despite the wind, we had a busier day today handling a total of 68 birds of 26 species. The highlight was our second Sharp-shinned Hawk of the season – a young male.
Banded 48:
1 Sharp-shinned Hawk
1 Mourning Dove
1 Downy Woodpecker
1 Northern Flicker
1 White-breasted Nuthatch
1 Winter Wren
3 Eastern Bluebirds
1 Swainson’s Thrush
4 American Robins
1 Gray Catbird
9 Cedar Waxwings
1 Blue-headed Vireo
1 Nashville Warbler
3 Magnolia Warblers
1 Western Palm Warbler
2 American Redstarts
1 Common Yellowthroat
9 Chipping Sparrows
1 Song Sparrow
1 White-throated Sparrow
1 Eastern White-crowned Sparrow
2 House Finches
1 American Goldfinch
ET’s: 43 spp.
NOTE: Nancy will start Northern Saw-whet Owl banding tomorrow (Wednesday night Please be aware that Ruthven’s AGM starts at 7:00 (with a great speaker on mapping northern rivers) and Nancy will open nets and start the call tape after that. She will also be opening nets Friday night as well. Please remember that there’s no guarantee that any owls will be caught…..but it’s fun just to be there.
Rick