Saturday, July 12, 2008

Mountain or Mole Hill?

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.


Anonymous said...

It is important to note that these calculations are based off of 11.49 acres of production and do not neccesarily represent the avian influence in the county. Addressing the issue of songbird damage - Robins are the worst offender, with finches a close second. It has been argued that songbirds are worse than starlings for crop loss. Fruit pecking is the biggest concern among all species, but knocking fruit off of branches by perching on them is the biggest factor. Crows are also a species that needs to be addressed. Their weight, intelligence, and social habits make them a problem species. They knock pounds of fruit off with ease and frequent fields in flocks and in solitary scouts. I would add them to the watch list. As you admit, counting is extremely subjective but in this case the problem is where the bad luck will fall. I will concede that your numbers are probably more than accurate for the day you counted. But what about the day when a flock moves through? The nature of this problem is that flocks can occupy a field faster than the grower can react. Prevention and proactivity are the only real protection strategies.

The comments comparing bird predation against machine harvest losses are also not compatible. Growers are not pleased with any current method of machine harvest losses, yet are forced to employ this method as opposed to employing a vast and expensive labor force that sustains losses of its own. It is sad to consider that growers should consider any loss as resonable. Calculating any losses as percents should include the reality that there are 99 other "reasonable" and "acceptable" losses incurred during the growing season. These add up to no margin for the grower. Farming is a business. Shrinkage is not acceptable to any viable business, growers should be no less exempt than the next industry.

CS said...

Thank you for your comments.

Remember I am only working this "thing" in this one field. However one wants to extrapolate to further reaches in the county is their choice.

I agree robins are a significant offender. What I am disputing is what sort of strategies are effective in repelling them? I have observed over the past 3 seasons, their impressive tolerance to just about any repellent threat. In-fact, have watched them sit on the nearest row-post to an Lp cannon, and only fluttering their feathers as it went off! The others simply remain where they were, in the bushes or on the ground.

Crows? Well in the past 3 seasons, I can not recall seeing one crow in the field. Have seen a few fly over, but not in the field. You can add them to the watch list, but at least in this one field, they have not come even close to inflicting the sort of havoc you describe.

Granted things can change rapidly just as you state, i.e., a starling flock moving in with speed and impact. If "prevention and proactivity" are simply automatically turning the cannons on early morning to late evening, 24/7, I would argue THAT is precisely THE wrong thing to do. I have seen this over and over again during 2005 and 2006. Once the flock you cite arrives, with such "preventative" devices having been operational for even weeks before the deluge, the Starlings are very very resistent to the cannon's threat. I have seen and heard, cannons going off on a regular cadence 6 am - 8 pm, 3-shots per every 3-4 minutes, 24/7; with squawkers going; with the grower riding up and down the rows on an ATV - WITH a flock that almost laughs at this.

Being present in-field for as much of the 50-day period as possible, will provide the grower with rapid response abilities. If they are not there monitoring, especially during the last 30-days, they invite disaster.

The "losses" statements of mine were not to say say anything is acceptable. But let's put this into perspective: 1.42% vs 10% is huge! For nearby neighbors to have to endure the horrendous impacts of cannon explosions to save 1.42%, while the picker machine drops 10% on the ground with every pass - well in my judgment THAT does put things into perspective.

I agree with you that a business is required to minimize it's costs (losses). Yet that never gives the business to in it's regular course of opertion, to knowingly and regularly inflict severe harm upon others for the sake of the bottom line.