It should describe a continuing professional engagement with an intermittent deployment pattern, name the forestry activities, state the period and the remuneration, and identify who supervises the work. A letter written around a single field season creates a gap the moment that season ends.
Write the letter around the engagement, not the season
The commonest drafting error in seasonal cases is a letter that reads like a short contract: dates in the spring, a description of one block, and nothing else. That letter supports one admission and then stops supporting anything. A better letter says that the company retains the forester to provide professional forestry services on a continuing basis, that deployments are expected in stated windows totalling a given number of weeks a year, that the engagement runs for a defined term, and that a named forestry manager directs the work.
It should describe silviculture prescription, timber cruising and stand assessment in professional terms rather than as field labour, since the distinction between a forester and a forestry technician is exactly what the entry turns on. Attach the retainer agreement if one exists, and keep each season's assignment memo in the same folder. Hypothetical example: a Hope landscape architect is retained to prepare a U.S.
campus planting plan, while the client expects her to make later site visits. The first review matches her landscape-architecture credential to the listed profession and tests whether the letter identifies the U.S. engager, duties, pay, and period.
Her diploma and transcript settle qualification; the signed scope and later change orders settle the continuing-work issue. A vague letter that says only “consulting” leaves an officer unable to see either the professional role or the employer relationship.