What lifts this above co-occurrence is that one lineage was enriched in two places at once, in the birds using dense feed stations and on the stations themselves [5][6]. Pigeons and doves are the group in which Trichomonas gallinae is established worldwide, and in which it threatens turtle doves [9]; the songbirds sharing farm feed are the group in which it turns lethal [10]. Screening hosts and surfaces at the same sites [8][3] is the design choice that lets the authors call resource-mediated transmission strongly evidenced [18] rather than merely consistent with the data. Dunn said the parasite proved far more widespread than the team expected, and that food and water look central to how it moves [16].
Then there is the size of the thing those ratios sit on. Thirty-nine percent of 51 sampled resources works out to roughly twenty positives [20], spread across twelve farmland sites in two countries [3]. The phys.org account of the Molecular Ecology paper [1] does not report how the 363 birds divided between high-density stations and natural seed [22], so the bird-level contrast has an unreported denominator as well. Ratios built on cells that small can move when a handful of samples flip, which is why the direction of the finding carries more weight here than the exact multiplier attached to it.
The number that will travel is the one in the write-up's opening line: birds three times more likely to catch a parasite from these resources [19]. The near-threefold gap in the reported figures belongs to the sites, and the birds' gap is the smaller one [21]. There is a second slippage in "more likely to catch". What was measured is prevalence, the share of birds and surfaces carrying the parasite at sampling [4], and a prevalence ratio is not a rate of acquisition.
Gardens are where most people meet this parasite, and earlier work had already pointed at shared food and water there [11], but the sampling in this study was farmland [3]. The RSPB's request that people feed seasonally and safely [14] sits comfortably alongside the finding without being tested by it. On farms, the change the authors ask for [13] has a worked precedent: low-density seed provision trialed for turtle doves is already part of the Operation Turtle Dove package [15]. The work was done with the RSPB, Natural England and the University of Sheffield [2], so the route from result to scheme guidance is short.
What none of this weighs is the other half of the ledger. Supplementary feeding is widespread on farms precisely because it is meant to support endangered birds and sustain gamebirds such as pheasants [12], and what this study measured is parasite prevalence, not fledgling numbers. The change the evidence supports is spreading the feed thinner. That recommendation does not ask anyone to put out less of it.
