Advanced options
Bulk bags (12.5-25kg) halve the per-kilo price of the little supermarket pouches: sunflower hearts are the crowd-pleaser with no husky mess. Hygiene beats quantity: feeders scrubbed fortnightly, food refreshed rather than topped eternally, since dirty feeders spread trichomonosis (the disease behind the greenfinch crash). Feed year-round but ease off whole peanuts in fledgling season.
What The Bird Food Calculator Works Out
- Per week: feeders x fills per week x capacity, converted to kilograms. Two 500 g feeders refilled three times a week move 3 kg of seed, which is 150-plus kilos a year before you have noticed.
- Per month: the weekly figure x 4.345 (the average weeks in a month), with how long a 12.5 kg sack lasts underneath. Sacks of 12.5 kg and 25 kg are the standard sizes in the online bird-food trade.
- Yearly cost: 52 weeks of seed at GBP 2 per kg, the bulk price for sunflower hearts, the husk-free crowd-pleaser that goldfinches, tits and robins agree on. Nyjer for finches and whole peanuts (meshed, and eased off in fledgling season) price higher; cheap "filler" mixes betray themselves by the wheat the birds kick to the floor.
- Seed price and sack size (advanced): edit the GBP 2 per kg assumption and the sack size you actually buy. Sunflower hearts run GBP 1.80 to GBP 2.50 per kg in 20 kg sacks; premium no-mess mixes GBP 2.50 to GBP 3.50. The sacks-per-year card is rounded up to whole sacks.
- Supermarket pouch comparison (advanced): the same kilograms at pouch prices, typically GBP 4 to GBP 6 per kg, with the annual saving from buying in bulk. For most gardens the saving is well over GBP 100 a year.
- Fat balls or suet blocks (advanced): how many you put out a week and what each costs (GBP 0.20 to GBP 0.40 in boxes of 50). Fat products cover winter's calorie cliff and are the second line in most bird budgets.
- Spillage and waste (advanced): adds a percentage for what ends up on the ground, kicked out by birds or taken by squirrels. 10% to 20% is realistic for open feeders; a seed tray under the feeder cuts it and keeps the rats away.
- All-in per month and per feeder per year (advanced): seed plus fat balls as a monthly budget line, and the seed cost each feeder accounts for, which is useful when deciding whether a third feeder is worth it.
- Hygiene and habitat: trichomonosis spread at dirty feeding stations drove the greenfinch crash, so scrub feeders fortnightly, rotate positions, refresh rather than top up, and pause feeding if sick birds appear. Planting (teasels, seed-heads, berrying shrubs) and a refilled birdbath feed and draw more species across a year than any sack.
Guidance: RSPB.