What's the impact of song birds (excluding Starlings) on blueberry fruit losses? I ask this because I have observed some growers who are, in my opinion, over reacting to the presence of such birds in their fields. This reaction, again in my opinion, significantly risks creating habituation conditions for the main villains: hoards of Starlings.
We need to know what the song birds contribute to fruit losses. And we need to know what these losses compare to as to the field's standing inventory of berries.
So on the field I have been working, this is what I have discovered and observed.
There are 17 rows (1300 feet) with 6621 older plants, each averaging 1146 blueberries per plant.
There are 25 rows (600 feet) with 4062 older plants, each averaging 1146 blueberries per plant.
There are 10 rows (1300 feet) with 2665 younger plants, each averaging 688 blueberries per plant.
[Yes, I know you're asking: "Did you count all those berries?" Nope. I did count the berries on 5 representative plants...and then factored up from there. Yes, I know, scientifically that was not technically a statistical sample. My effort was not preciseness, but more of just getting a sense of scale. If someone want's a "Florida recount", be my guest and we'll re-crunch the numbers.]
With that being said, we find the following:
First group has 7,587,666 blueberries
Second group has 4,655,052 blueberries
Third group has 1,833,520 blueberries
Total equalling a 14,076,238 blueberry standing inventory as of 7/11/2008.
We now have some idea for how many berries are in the field, to which we can compare the percentage of losses by song birds (again excluding Starlings).
I have been in this field every day, multiple times (as this blog site shows), and have been recording bird observations (type and number). Choosing yesterday's observations, there were between 5:30-7:00 pm:
8 - Robins
5 - Purple finches
3 - Ceder waxwings
A total of 16 birds.
Do I think this represents all the song birds visiting the field on this day? No. Of course there were more. So let's assume there were 6 times more birds (16 x 6=96 song birds).
So with the 96 birds, we need to estimate the numerical loss of berries per bird. Who knows this? Perhaps Einstein or Rachel Carson. Short of having emperical data on such, let's assume each bird eats, destroys or removes 10 berries from this field per day. The math indicates that 960 berries are lost per day.
With this, what then are the percentage losses as compared to the field's standing inventory?
Okay some big number crunching now: 960 divided by 14,076,238 = 0.0000682 or 0.00682% loss per day. If these losses continue for a 50-day season, we discover 0.0031 or 0.31% loss per growing season.
Now let's say I am way off on how many actual song birds are really in the field; and, how many actual berries they destroy per day.
Say there were 200 song birds present yesterday, who each destroyed 20 berries each per day. This equates to 4,000 blueberries loss per day.
Again big (or is it small) number crunching, 4000 divided by 14,076,238 = 0.000284 or 0.0284% loss per day. For the 50-day season, we have 0.0142 or 1.42% loss per growing season.
So we can see that within reason, this field can expect between 0.31% and 1.42% losses from song birds this season.
My point, what am I driving at? It is my contention when a blueberry grower over reacts to very limited song bird predation pressure, and deploys ANY repellent device or strategy, ramped up as if the field is being overrun, he risks the danger of setting habituative conditions that may very soon come back to haunt him (i.e., hoards of Starling flocks).
Putting out loud, explosive devices at this stage in bird pressure is unwarranted. It really is a "Making a Mountain out of a Mole Hill". It's a "Majoring on minors vs majoring on majors".
Additionally, I challenge the level of effectiveness of these or ANY devices on repelling song birds, this from my own multi-season in-field observations.
And lastly, really is it worth it to press nearby people and neighbors with the loud, startling noise, when fruit losses are very minor? And this particularly in-light of the fact that current machine picking losses are around 10% as fruit falls between the picker to the ground!
Stuff for thought and reflection. Hope it contributes to better understanding.
REMEMBER: The villain is the Starling. It is not the grower.