In the serene forests of the Dundas Valley and Iroquoia Heights, a quiet battle has been waging for years.

On the one side, Hamilton Conservation Authority workers are planting seedlings to try to ensure there will be big trees in the future.

And on the other side, hundreds of deer are eating away at these efforts — especially in the winter.

The end result is that if workers don't stay one step ahead of the animals, the forests of the Dundas Valley and Iroquoia Heights will likely decline for future generations.

On Thursday the conservation authority's effort will take to a helicopter in a reconnaissance mission — with assistance of the Ministry of Natural Resources and Forestry and Ontario Parks — to find out how formidable an opponent they face.

The conservation authority has done this twice before. In 2009 when they found 505 deer in the Dundas Valley and 102 in Iroquois Heights. In 2013 there were 379 and 58, respectively.

"In order for us to get a better idea of what we are seeing on the ground, we like to go up in the air and actually count the deer," said Lesley McDonnell, a terrestrial ecologist at the Hamilton Conservation Authority.

The information will be blended with vegetation surveys researchers have done on the ground.

She says surveys in the past have never led to culls of deer, but they have encouraged conservation authority workers to take special steps.

Often, McDonnell said, fences are put around newly planted seedlings. In other cases far more mature trees are planted, maybe a couple of metres tall, that can withstand deer.

For the past several years, Haudenosaunee have taken part in a deer hunt in the Dundas Valley, but the last one from Nov. 12 to Dec. 6 last year fell well short of an agreed limit of 60. In the end about 15 deer were killed. Weather and the difficulty getting around in winter were cited as factors in the low numbers.

mmcneil@thespec.com

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