Nest box tales: Duckling surprise!
It’s moments like these that make my nest box efforts feel so worthwhile, particularly over the past year.
During the month of January despite two above 40 degree heatwaves, with our local average monthly temperatures being 6 degrees above the long-term average, including four (never previously recorded) consecutive days above 40 degrees, most of the Wood Duck eggs from the two nest boxes successfully developed and hatched as healthy ducklings at the end of last week.
On Saturday morning while checking out a new resident Eastern Brown Snake, I looked out at our dam to see Wood Duck mum, dad, and 19 day-old ducklings following behind! The ducklings had jumped from their nest box on Friday morning according to the wildlife cameras that I rushed to check shortly after. These are from the same nest box as our last successfully hatched clutch of Wood Duck eggs earlier this season. 21 eggs were laid (probably by a couple of females), 19 hatched.
I then discovered that the smaller clutch of Wood Duck eggs had also hatched and abandoned their nest box on Thursday evening according to wildlife cameras. This family came to visit our dam on Sunday afternoon. I had a hunch that this was a first-season nesting family, as the eggs were significantly smaller than other Wood Duck eggs I’ve seen in nest boxes previously. Given dad’s hilariously flighty responses to the falling ducklings (first video), I’d say this was a totally new experience for him!
This is such a rewarding conclusion to the nesting season for our feathered nest box residents.
Some more recent background and learnings:
On December 13th-14th, there were large storms causing significant rainfall resting in flooding for some areas locally. This triggered interest in late-season nesting by several Wood Duck pairs, with the first eggs laid within a few days of this rainfall in three of our nest boxes. One nest box was abandoned before sitting began, however with a full clutch of eggs laid.
The other two nest box Wood Duck females trooped on, with embryos in eggs somehow surviving numerous days where temperatures were well above the optimum duck egg incubation temperature of 37.5 degrees C.
I purchased some Thermochron temperature loggers after the four-day 40 degree heatwave, and installed these in four same-sized small parrot nest boxes facing NE, SE, SW and NW, and also one Thermochron hanging on the tree on the least-sunny side to record the ambient woodland temperature.
These recorded the inside-nest box and also outside temperatures during the second 40 degree heatwave, to give me an idea of the temperature differences between nest boxes installed at different orientations.
From this season, I know that Crimson Rosella chicks can survive a heatwave of four consecutive 36-37 degree days, but can’t survive four consecutive days of 40-42 degrees [36.5, 40.1 (2 chicks dead), 41.6, 41.4, 40.1 (last chick dead), 36.0]. It is likely that even 2 degrees cooler may enhance chances of survival in a nest box during a hot spell, if such a difference can be gained with better nest box orientation.
From my little experiment and temperatures logged by the Thermochrons, there looks to be a small difference in the maximum temperatures reached, and also the duration of max temps, depending on nest box orientation. South East is the winning orientation, with maximum temps 1-3 degrees less than the max for other orientations.
This temperature difference I think, could have the potential to be life-saving for those very hot days. Similar results are found by other studies, however the temperature differences I would expect, would vary depending on the specific environmental conditions.
Heat for our bird nest boxes is going to be an ongoing challenge to solve, for a number of reasons.
The native vegetation on our property is an open-canopy grassy woodland regrowing from being completely cleared land for 25 years. Open grassy woodlands by nature, are not very shady. Most of our young regrowth trees are small in diameter. This means that tree trunks do not provide shade for installed nest boxes for much of the day, as large-girthed trees would. Many of our little scribbly gums and brittle gums are a little smaller, to just a little larger in diameter as the installed nest boxes.
To prevent predation of bird eggs, chicks and also adult birds by our numerous resident Sugar Gliders and Brushtail Possums, I must install the bird nest boxes on tall, straight (possum-guardable) trees, that do not have nearby cover of trees and shrubs that a possum can use to cross to the nest box. In comparison the possum nest boxes are installed on trees shaded by stands of Black Wattle, they do not suffer the Summer heat so much!
So I am aware that heat is going to be a challenge we will increasingly struggle with for our bird nest boxes, as future climate predictions for this region are of warmer, wetter Summers, with longer and more extreme heatwaves. Winter and Spring are predicted to become drier.
The nesting by birds such as Rosellas and Wood Ducks are often triggered by significant rainfall events in dryer localities such as ours, indicating that they will likely nest later in the year and during the hotter months (November-December rather than September-October) given future local climate predictions. Winter and Spring were exceptionally dry during the past year in our region, with interest in nesting by birds apparent only in late Spring after the first significant rainfall in months.
I see this anomalous twelve month period with weather events apparently very similar to predictions of our regional future climate predictions (dry Winter and Spring, very hot and more wet Summer with more and hotter heatwaves), being a good road-test of nesting challenges and successes for our local birds with the impacts of climate change. Given the successes we’ve had this nesting season, with only losing one family of nest box chicks (Crimson Rosellas) despite the significantly hotter than normal weather, the future looks promising in spite of the apparent challenges.
Meanwhile I’ll continue to enjoy figuring out solutions to overcome some of these challenges.
I have also just purchased tree climbing kit, so will be installing nest boxes designed for larger parrot species much higher up in the trees during the coming weeks. This will hopefully interest Gang Gangs, Galahs, King Parrots, Yellow-tailed Black Cockatoos and a few other large parrot species that occur in the local area. We shall see.
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This year’s nest box tally:
1 White Throated Tree Creeper chick
2 surviving Kookaburra chicks
4 Eastern Rosella chicks
3 + 2 Crimson Rosella chicks
8 + 19 + 6 Wood Duck ducklings
2 + 2 + 1 Ringtails, mums & bubs & one solitary
4-5 Sugar Gliders in one box
1 x raided Crimson Rosella nest (eggs)
3 Crimson Rosella chicks in one nest box died from heat
5 x raided Wood Duck nests (eggs, by Ravens & Brushtails)
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Last year’s nest box tally:
1 White Throated Tree Creeper chick
2 Kookaburra chicks
3 Wood Duck ducklings
6+ Brushtails in different boxes, different days
1 + 1 + 1 + ? single Ringtails in different boxes
4-6 Sugar Glider family in one box
5 x raided Crimson Rosella nests (eggs)
6 x raided Wood Duck nests (eggs, one Brushtail tried to kill sitting mum)
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First year nest box tally:
No successfully nesting birds
6+ Brushtails sleeping in every box they could fit into, on different boxes on different days
1 + 1 single Ringtails using one box each, most days
4-6 Sugar Glider mum & bubs in one box