Picking up were we left off earlier in Mountain or Mole Hill?, now using updated numbers from the past 30-days (July 6-August 5, 2008, less July 18 with no observations), let's see what sort of berry losses were likely to have occurred this past growing season.
Remember the first posting Mountain or Mole Hill? only relied upon a set of figures based on one day’s observed bird numbers, and we used a 50-day period as the season. Below the bird numbers come from observations made during both a 30-day period which was this season's length.
During these 30-days, I made 68 observations while in the blueberry field which averages 2.26 observations/day. The grand total number of birds observed (all species) that were present in, arriving or departing the field equaled 941 during those 68 observations.
In an effort to average out the number of birds throughout the 30-day period and thus come to some sort of conclusion how many birds were present at any given time, here's how I did that:
The number of birds per observation = 13.8 [941/68=13.8]
The number of birds per day = 31.3 [13.8 X 2.26=31.3]
For now, let us assume that these 31.3 birds are all that has impacted the berries each of the 30-days, each day.
Assuming each bird destroys 10 berries per day, the berry loss per day would be 313 berries per day. Total losses for 30-days would be 9,390 berries.
Even though I think we have a pretty good idea for numbers of birds in the field at any given time, lets say I underestimated this number by 3.
Now, let us assume there are 93.9 birds in the field. Each destroys 10 berries per day. The daily loss would be 939 berries. Total losses for 30-days would be 28,170 berries.
Going back to the assumed field’s standing inventory equalling 14,076,238 berries (see earlier post), let’s calculate what sort of percentage loss these 93.9 birds have on the field.
28,170 berries lost during 30-days divided by 14,076,238 total inventory = 0.002 or 0.2% loss for the 30-day period.
Okay let’s make it even worse, way worse. We will increase the impact 10 times (either by number of birds, or the same number but these gluttons eating 10 times the fruit…serious digestive problems to follow for sure). Based on this, the 30-day total loss will be 2.0%.
REMEMBER: This last number has increased from ACTUAL bird observations by a factor of THIRTY (30) TIMES!
Within reason we have overall bird predation impact between a range of: 0.2% a likely and moderate estimate, to 2.0% a unobserved worst case and unlikely scenario.
Again...all I am trying to do here is give EVERYONE some sense of what the scale is when it comes to berry loss by birds. Especially when the impact of cannons is real, invasive and harmful.
Let me add another poignant consideration.
During those 68 in-field observations, of the total 941 birds in the count, 537 were Robins and 179 (19%) were Starlings. And of those Starlings, 117 were observed on one day (July 28th). If you consider that day real, but unusual and disregard it, then observed for the remaining 29-days were only 62 Starlings. Just 62!
Either way, you do the math to find out what the fruit-loss was for this season for this field by Starlings! Try it you'll like it...hey Mikey!
The poignant point is this: Robins do not respond to loud explosive repellent devices. This is my 4-year personal observation. Even directly targeting (but missing on purpose) incoming robins and shooting off a shotgun - does not deter them! Shooting over the field does not work. Blasting Lp cannons does not work. Nothing works except perhaps a taste repellent (Migrate-RejexIt) or netting.
So if growers face the same sort of number scenarios as above: Starlings a minor component of predation, and Robins are the majority, and cannons applied automatically and indiscriminately ... I ask for what? What are we trying to do? For what good? And placing at risk the health and well-being of the rural community? Why?!
I am not addressing conditions of the hoards of Starlings, which may be out there somewhere. I am addressing the real conditions found in fields like described in this blog.
More on this later. But thanks for plowing through this with me.
REMEMBER: The villain is the Starling. It is not the grower.