Core Income for the quarter ended March 31, 2013, was $67.5 million. "Core Income" represents a non-GAAP measure and is defined as net income excluding impairment losses, gains or losses on sales of securities and early termination of derivatives, unrealized gains or losses on derivatives and certain non-recurring expenses. Core Income may differ from GAAP earnings as GAAP earnings include the unrealized gains or losses of the Company's derivative instruments and the gains or losses on Agency Securities.
For the purposes of computing GAAP net income, the change in fair value of the Company's derivatives is reflected in current period net income, while the change in fair value of its Agency Securities is reflected in its consolidated statement of comprehensive income. Due to the rise in interest rates during the quarter, the corresponding unrealized gain on derivatives was $16.3 million. GAAP net income for the first quarter of 2013 was $102.3 million, including realized gains on the sales of Agency Securities of $18.5 million.
DividendsThe Company paid dividends of $0.08 per Common share of record for each month of the quarter, resulting in payments to common stockholders of $79.8 million. The Company also paid monthly dividends of $0.17 per outstanding share of Series A Preferred Stock resulting in payments to Series A Preferred stockholders of $1.1 million. For the quarter ended March 31, 2013, the Company paid initial dividends of $0.25 per outstanding share of Series B Preferred Stock, resulting in payments to Series B Preferred stockholders of $1.4 million. The Company had estimated taxable REIT income available to pay dividends of $86.0 million in Q1 2013. Per Share Amounts Per Common share amounts are net of applicable Preferred Stock dividends and liquidation preferences. The denominators used to calculate per Common share amounts as of March 31, 2013 and for the quarter then ended reflect the dilutive effects of unvested stock awards. Such effects are not material.